3Ji» - 110"
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Gla^^l^^^ty Library

•^^B 1997

GUL 92.18

REPORT

OF THE

MALARIA EXPEDITION

LONDON :

GEORGE PHILIP & SON 32 FLEET STREET

LIVERPOOL :

PHILIP SON & NEPHEW 45 to 51 SOUTH CASTLE STREET

LIVERPOOL SCHOOL OF TROPICAL MEDICINE— MEMOIR II.

REPORT

OF THE

MALARIA EXPEDITION

OF THE

LIVERPOOL SCHOOL OF TROPICAL MEDICINE
AND MEDICAL PARASITOLOGY

BY

RONALD ROSS, D.P.H., M.R.C.S.

LECTURER IN TROPICAL MEDICINE UNIVERSITY COLLEGE LIVERPOOL

H. E. ANNETT, M.D., D.P.H.

DEMONSTRATOR IN TROPICAL PATHOLOGY

E. E. AUSTEN

ZOOLOGICAL DEPARTMENT BRITISH MUSEUM

WITH SUPPLEMENTARY REPORTS

By Major G. M. GILES, M.B., F.R.C.S., Indian Medical Service
And R. FIELDING-OULD, M.A., M.B.

M'lTH ILLUSTRATIONS PLATES AND MAPS

Price los. 6d. net

AT THE UNIVERSITY PRESS OF LIVERPOOL 1900

PRINTED AT THE UNIVERSITY PRESS OF LIVERPOOL
No. ^. Feb., 1900, 1500 Copies printed.

RIGHT HONOURABLE JOSEPH CHAMBERLAIN, M.P.

Her Majesty's Principal Secretary of State
FOR THE Colonies

Who in his own City has founded a University

AND

Directed Research to the alleviation of Tropical Maladies
throughout vast provinces of the Empire

This Report upon the Prevention of Malarial Fever
IN West Africa is Respectfully Dedicated

BY THE

LIVERPOOL SCHOOL OF TROPICAL MEDICINE

Digitized by the Internet Archive
in 2015

https://archive.org/details/b21458674

ISSUED BY THE COMMITTEE

OF THE

LIVERPOOL SCHOOL OF TROPICAL MEDICINE
AND MEDICAL PARASITOLOGY.

j- Council of University College.
Senate of University College.

COMMITTEE.
Alfred L. Jones, J. P., CJuiirma,,.

Wm. AdamSOn, Fice-Cliatrman.

R. T. Glazebrook,
Charles W. Jones,
R. W. Boyce, 1
A. M. Paterson, )
W. Alexander,
W. Carter,

J. O. Strafford, Hon. Tn-asunr, ]

]■ Ch.imber of Commerce.

E. Adam, )
J. W. Hughes, )

, Steamship Owners' Association.

Charles Booth, Jun., i
Col. Goffey, I .

, Shipowners' Association.

Jos. Chadwick, )

I Royal Southern Hospital.

A. H. Milne, -SV.

ac5nowle^onlcnt0.

In publishing this Report the Committee wish to express their thanks, for assistance
rendered in furtherance of the objects of the expedition, to the Right Honourable Joseph
Chamberlain, Secretary of State for the Colonies; to Professor E. Ray Lankester, F.R.S.,
Director of the Natural History Department of the British Museum ; to the British Medical
Association ; to H. E. Major Nathan, R.E., C.M.G., Acting Governor of Sierra Leone;
to H. E. Sir Frederic Hodgson, K.C.M.G., Governor of the Gold Coast; to H. E. Sir
JVilliam MacGregor, M.D., K.C.M.G., Governor of Lagos; to Colonel Burke, D.S.O.,
Commanding H. M. Forces in Sierra Leone; to Major N orris, D.S.O., and the Officers,
1st Batt. West India Regiment, Sierra Leone ; to Drs. Strachan, Prout, Henderson,
Renner, Berkeley, and Chalmers, of the West Coast; and to Major G. M. Giles, LM.S.,
for kindly undertaking part of the work of Mr. Austen.

'•The present opportunity has been taken for recording some previous observations on
the subject made in India by one of the members of the expedition.

ALFRED L. JONES,

Chairman.

CONTENTS

I. PRELIMINARY. page

1. Introduction j

2. Objects of the expedition 2

3. History of the expedition -------- 2

4. Terminology employed ^

II. FREETOWN, AND FEVER STATISTICS.

5. Description of Freetown -------- ^

6. Statistics - 5

III. H^MAMCEBIDyE IN FREETOWN.

7. The Hjemamoebida; in intermediary hosts ----- 8

8. Methods for ascertaining definitive hosts ------ g

9. Definitive hosts in Freetown - g

10. The Hasmamoebidas in the definitive hosts - - - - .

IV. BIONOMICS OF THE CULICID^ IN FREETOWN.

11. Differences between Culex And. Anopheles - - - - - - 15

12. Breeding-places of Culex - - - - - - ' - 16

13. Breeding-places of v/»5//5<'/fi 16

14. Distribution of Anopheles in Freetown - - - - - - 18

15. Bionomics of ^OT/z^^/^j larvae - -

16. Bionomics of adult 20

17. Bionomical questions still requiring investigation ----- 24

18. Source of the Wilberforce - - - - - - 25

V. DISCUSSIONS.

19. Questions regarding the parasites - -- -- --26

20. Cause of occasional failures in direct cultivation ----- 29

21. Known facts about malaria explained -------30

22. Are other insects besides yf«&//^^'Z?; hospitable to the human Hasmaniffibids ? - 31

23. Are other vertebrates besides man hospitable to the human Hsmamoebidas : - - 32

24. Is the Life-history of the H;tmamcebida; fully known - - - - 33

VI. PREVENTION.

25. Measures indicated - --37

26. Precautions against the bites of gnats - - - - - 38

27. Operations for reducing the numbers of Anopheles ----- 40

28. Under what conditions do operations agains A7iopheles promise to be most successful 41

29. Recommendations -------- 43

VII. REMARKS.

30. Miscellaneous remarks -------- 45

ADDENDA.

1. Description of two species of Anopheles, by Major Giles, I. M.S. - - - 49

2. Observations at Freetown, Accra, and Lagos, by Dr. Fielding-Ould - - 51

REFERENCES.

PLATES AND MAPS.

REPORT OF THE MALARIA EXPEDITION

OF THE

LIVERPOOL SCHOOL OF TROPICAL MEDICINE
AND MEDICAL PARASITOLOGY.

I. PRELIMINARY.

I. — Introduction. — Tlie H^mamcebid^ are a group of unicellular parasites of the
red blood-corpuscle, found in man and in certain kinds of monkeys, bats, birds, and, perh.ips,
frogs. The group derives great importance from the fact that the human species are the
cause of malarial fever.

We owe the discover^' of these organisms to Laveran, Danilewsky, Koch, and Dionisi ;
and are indebted to Laveran, Golgi, Romanowsky, MacCallum, and others for our knowledge
of their life-history and structure within the vertebrate hosts.

Following upon these discoveries, it remained to ascertain the life-history of the group
outside these hosts ; but all efforts to cultivate them or to find them in external nature were
attended at first with failure. In 1883, however. King adduced a number of reasons in
support of the view that gnats are connected with the propagation of malarial fever [i].
Next year Laveran expressed the opinion that the parasites discovered b)' him may undergo
further development in gnats [2]. In 1894 Manson independently came to the same con-
clusion ; chiefly on the ground that some forms of the parasites (gametocytes) emit certain
motile filaments (microgametes) after the blood containing tliem is drawn from the host — a
phenomenon which could be explained only by the theorv that the parasites migrate into
suctorial insects [3, 4]. Koch, Mendini, and Bignami have also adopted the gnat-theory of
malaria on various grounds [12].

Working in India upon Manson's induction, one of us, after numerous negative
experiments with several species of gnats of the genus Culex, succeeded in cultivating one of
the human Hasmamoebida; in two species of gnats of the genus Anopheles (dappled-winged
mosquitoes) in 1897 [5] ; and next year completed our knowledge of at least one c\ cle of
the life-historv of this group of parasites by following the development of Hamamceha relkta
of birds in gnats of the Ciilex pipiens type [6], and by communicating the infection from
diseased to healthy birds by the bite of these insects [7]. This work was confirmed by
Daniels in 1898-99 [8].

2

REPORT OF THE MALARIA EXPEDITION.

In 1897 MacCallum had already supplied an important fact in the life-history of the
group by demonstrating the sexual nature of certain forms (gametocytes) of the organisms [9].

At tlic end of 1898, Kocli and Grassi, Bignami and Bastianelli, almost simultaneously
confirmed these observations. It was found that in Ital)', as in India, the human species develop
in gnats of tlie genus Anopheles ; and the Italian observers finally succeeded in infecting healthy
human beings by the bite of previously infected insects of this kind [10, 11].

The results of tliese investigations have been accepted by Ray Lankester, Laveran,
Manson, MetchnikofF, and others ; and a full history and bibliography of the subject has been
published by Nuttall [12].

To sum up ; although some points of importance still require investigation, it has been
shown that certain species of gnats are definitive hosts of the Haemamoebida; ; that the parasites
are conveyed from diseased to healthy vertebrates (intermediary hosts) by these insects ; and
that the definitive hosts of the human parasites are certain species of Anopheles [Section ^.].

2. Objects of the Expedition. — As soon as these facts were ascertained it became
necessary to enquire whether the discovery could not be turned to practical account for the better
prevention of malarial fever. The question was theoretically examined at length by one of us
in February [13], and again in May, 1899 [14]. From an early stage in his investigations in
India he had noted that, so far as his studies then went, gnats of tlie genus Anophe/es sometimes
appeared to breed only in comparatively small and isolated pools of water — a fact which
suggested that in some localities it may be possible to exterminate them without great difficulty.
Unfortunately his observations had not been exhaustive enough to enable him to speak with
confidence on the point ; while other students of the subject had not given it sufficient attention.

Hence the Liverpool School of Tropical Diseases undertook to open a special investigation
of the question ; and despatched an expedition consisting of ourselves to the West Coast of Africa
for tlie purpose. Our objects were as follows :- -

(i.) To find one or more species of insects hospitable to the human Haemamoebidae on
the West Coast of Africa.

(2.) To study the bionomics of these insects with a view to suggesting better modes of
prevention of malarial fever than those hitherto known to us.

It was not proposed that the expedition should remain in Africa for more tlian a few
weeks ; and it will therefore be understood that, owing to the siiort time at our disposal, we were
obliged to limit our investigations strictly to the matter in liand.

3. History of the Expedition.— Sierra Leone was selected for the field of the first
operations.

The expedition primarily consisted of (i) Major R. Ross, Lecturer in Tropical Medicine,
University College, Liverpool ; (2) Dr. H. E. Annett, Demonstrator in Tropical Pathology,
Liverpool School of Tropical Diseases ; and (3) E. E. Austen, Esq., Zoological Department,
British Museum.

REPORT OF THE MALARIA EXPEDITION.

3

We arrived in Freetown, Sierra Leone, on the lOth August, 1899 ; and speedily
succeeded in ascertaining that two species of gnats of the genus Anopheles found in Freetown are
hospitable to the human Haemamoebidre [Section III.]. The rest of our time was spent chiefly in
a study of the bionomics of these insects [Section IF.] ; and we left Freetown for England on the
27th September, after seven weeks' stay in the colony.

Our observations constitute the body of this report ; but before our departure from Sierra
Leone we were joined by Dr. Fielding-Ould, who was despatched by the Committee of the
School to continue our labours after our return. After we left, Dr. Fielding-Ould proceeded to
Accra and Lagos ; and his observations are given separately in the Addenda to this report.

We were also joined at Freetown by Dr. G. Van Neck from Belgium. Dr. Van Neck
was unfortunately taken seriously ill shortly after our departure, and did not return until
December.

4. Terminology Employed. — As regards tlie H;emamuebid;e, we adopt the morpho-
logical terminology and taxonomic nomenclature already used b\ one of us in consultation with
Professor Herdman, F.R.S. [15]. These will be found in tlie Discussiojis [paragraph 19] ; where
we consider the terminology further, and also give a sumniar\' of the life-]iistor\- and classirication
of the parasites.

As there is no difference between gnats and mosquitoes — tlie latter term being merel\- one
whicli is popularly employed for gnats in warm countries — and as this confusion tends to maintain
erroneous notions regarding tliese insects, we propose to abandon the word mosquito and use in
preference the old English equivalent gnat.

The terms tnalaria and inalarial fever are unsound, while pahidisni is inexact. We may
tlierefore venture to suggest tlie appellations hcemamcebiasis or gnat-fever for the disease wliich is
the subject of this report. They will at least serve to popularise more correct notions of tlie
malady than are implied in the word malaria.

( 4 )

II. FREETOWN, and FEVER STATISTICS.

Freetown from Mount Aureole, looking westwanl. Tower
Hill in tlie middle distance, and Wilberforce Hill in the
distance.

5. Description of Freetown. — Freetown, the Capital of the British Colony of Sierra
Leone, is situated approximately in Lat. 8° 30' N., and Long. 13" 15' W., on the northern shore
of a mountainous promontory. Close behind the town there is a semicircle of wooded hills rising
to a height of 3,000 feet above sea-level ; and the town itself lies mostly on areas of level ground
between them and the sea. 'I'he principal houses are built near the wharfs ; but from here the
suburbs reach backward between the spurs of the hills. Few houses of the town proper exist on
the slopes of the hills ; but numerous separate villages are found in the higher valleys above.

The soil of Freetown is derived from
a red laterite rock ; which lies at little depth,
and is exposed in man)' level parts ot the
town, as well as in water-courses, etc.

Tlie rainv season lasts from May until
October. Tlie average annual rainfall is 163
inches, the average humidity 75.0, and the
average temperature 80.0' F. [^paragraph 6'].

'Fhe citv contained 30,033 inhabitants
at the last census (1891). The population

consists mostly of natives (Christians, Mohammedans, Pagans), but there is also a colony of
Europeans.

The streets are open spaces between
the houses, generally fringed with grass, un-
paved, and undrained, except by roadside
ditches ; but gutters exist in the best part of
the town, and occasionally elsewhere. Most
of the streets are sloped, but a few are almost
level.

The liouses are built mostly of wood,
or consist of a superstructure of wood on a
masonry foundation. They are often two
stories high, and are generally divided from

2. Street in Freetown, showing ,litch at the side. ^^^^ ^^^^'^^ ^^^„ ^^^^^ ^^^^ .^.x^^n^

in the manner of villai. As a rule the rooms are very small for tropical habitations.
Tiiere is an excellent water-supply brought fVom the adjacent hills in pipes.

REPORT OF THE MALARIA EXPEDITION.

5

Surface and storm-water drainage is carried mt)stl}' in the roadside ditclies, but mountain
torrents on their way to the sea occasionally intersect the level areas on which the town is built.

There is no sewage drainage, nor removal system for night-soil. Deep pits, or ratlier
wells, covered by a privy and seat, are employed. It is stated tliat the old pits are sometimes filled
up and new ones dug ; but so far as we could judge, drv earth is seldom used, except by the
Europeans and troops, and the system adopted seems to be a natural kind of septic-tank sj'stem.

Wells for drinking-water are not generally in use.

Horses and wheeled traffic are rare. Those who do not walk are carried by native bearers
in " hammocks."

The troops, which belong mostly to the West India and West African regiments, are
housed much better than the civil population. Their barracks are well-built wooden structures,
placed on the summits of four hills ; namely, on Tower Hill (400 feet), in the middle of the
town ; on Mount Aureole (800 feet) and Kortright Hill (1,100 feet), to the east of the town ; and
on Wilberforce Hill (600 feet), some distance to the west of the town [p/iotograph i and Map /.].

Civil patients are treated in the large Colonial Hospital, the Incurable Hospitals, Lunatic
Asylum, etc. Military sick have their own hospitals attached to the several barracks mentioned
above.

Mangrove swamps occur in some of the bays and creeks of the shore.

Collections of water suitable for. the larvas of gnats abounded in the town when we were
there (rainy season). Such collections could be divided into two classes ; namely, (1) collections in
vessels ; and (2) collections on the ground. The former occurred in tubs, pots, broken bottles, etc.,
in the vicinity of almost all the houses ; the latter chiefly in the roadside ditches and holes in
rock, and, almost exclusively, on areas of level ground.

6. Statistics-— It is usually impossible to obtain from statistics any exact information
regarding the actual number of infections of haemamoebiasis occurring within a given place and
period. The reasons for this are — (i) that the vast majority of attacks are not recorded ; (2) that
a large number of attacks which are recorded must be mere relapses, due to infections acquired
perhaps long previously and in other localities ; and (3) that the microscope is not generally used
for exact diagnosis. Similarly the mortality returns are apt to be vitiated, because (i) the infection
has often been acquired elsewhere ; (2) Europeans are frequently invalided when seriously ill ;
and (3) deaths of cachectics are often ascribed to immediate causes, such as pneumonia and
dysenter)'.

Military returns, though they are sometimes thought to be more trustworth\-, are open to
the same objections. Many soldiers do not come to hospital at all for slight attacks of fever ;
while others are frequently only "detained" in hospital for brief treatment, without being
"admitted" that is, entered in the returns. Thus we were informed of an instance in which
only one quarter of the cases of fever which came to hospital had been "admitted" and recorded.

The absolute figures are therefore not trustworthy ; but, by supposing the ratio of error
to be always constant, we may derive some useful comparative information regarding the amount
of fever prevalent in different places, and at different seasons.

6

REPORT OF THE MALARIA EXPEDITION.

We will content ourselves by giving a table extracted from the work of Major L. M.
Wilson, R.A.M.c. [i6]. The statistics are based on admissions to hospital among the troops in
Sierra Leone during seven years (1892-98), and on the meteorological returns of the same period.

Average monthly Admission rates among the troops, and average monthl\ Rainfall, Humidity, and
Temperature in Sierra Leone during seven years (1892-98).

Month.

Average admission rate per looo.

Average
Rainfall in
inches.

Average
Humidity.

Average
Temperature
in shade.

Non-European.

European.

January ...

S3

93

.80

70.2

80.8

Februarj-

47

99

.86

68.2

81.0

63

59

67 7

St 7
01./

April

86

106

4.36

67.3

81.6

May

99

325

14.08

75-3

80.3

June

128

347

18.62

77.1

79.2

M-

■

171

413

33-34

83.0

78.3

August ...

1.6

281

38.96

84.0

77-7

September

9.

'73

29.85

82.2

78.8

October ...

67

121

'4-63

79.1

79-4

November

72

125

5-41

75-0

80.5

December

64

92

1.26

71.9

80.7

Annual

1056

2134

163.41

75.0

80.0

Judging from these figures Wilson remarks, " The largest number of cases occur in
the middle of tlie rainy season." Thougli many of the cases recorded in the rains may be
relapses due to wettings, chills, etc., this can scarcely account for the quadruplication of tiie
admissions shown in tlie table ; and it would therefore appear that the period of fresh infections
sets in (or at least increases) with the rains, and ceases (or at least diminishes) with tltem.

Wilson also thinks that "The white troops suffer more in proportion than tiie black."
He gives the annual average death-rate of the white troops from malarial tever at 42.9 per
milk, as against 5.9 per mille for the black troops. Similarl)-, he tlnnks that "Eacli battalion
of the West India Regiment suffers exceptionally from fever the first year of its service on
tlie coast." Such differences point ratlier to variations in immunity, than to variations m
frequency of injection in the groups concerned.

It is hardlv necessary to compare these statistics of Sierra Leone with simitar figures
for many other stations in the empire ; but it will be instructive to give some ratios taken
from the Annual Report of the Sanitary Commissioner with the Government of India for 1897.

For the whole European Army of India during that year the admissions per mille of
strength for malarial fever were 420.1 ; and the deaths per mille were l.O — far below the

REPORT OF THE MALARIA EXPEDITION.

7

figures for Sierra Leone. But in the most malarious stations the admissions per villk reached
1500; and the deaths, 6.0, excluding "remittent fever."

For the whole Native Armv of India the annual admissions per m'lUe were 362.8 ; and
the deaths per m'llle^ 1.7. But in the most malarious stations the admissions reached 2230,
and the deaths, 6.8 per mi lie*

It is obvious that Sierra Leone is much more malarious than India taken as a whole
is ; though perhaps not much more so than some places in India.

A study of the Indian statistics shows, moreover, that the admissions for the disease in
that country have, roughly, the same dependence on rainfall as they have in Sierra Leone —
that is, of course, not on the total amount of rainfall, but on its seasonal variations. Indeed,
some of the most malarious military stations in India (Peshawur, Delhi, Lahore, etc.) have a
small total rainfall.

*As a rule, natives in India suffer more than Europeans do — at least to judge by statistics.

(8)

III. H^MAMCfc:BID^ IN FREETOWN.

7. The Haemamoebidae in Intermediary Hosts.— Duggan studied the human parasites
of Sierra Leone some years ago [17]. He found only Heemoynencn pnecox (with one exception — a
case of H(ema}Hceha v'lvax). Hctmomencn malaria: was not observed hy liim. He says " Crescents
were found in varying numbers in most of tlie cases." His results are based on the study of
" about 400 cases."

Our own examinations of the blood of patients were made solely with a view to obtaining
a basis for further researches as to the definitive hosts of the parasites ; and it will be understood
that we contemplated no morphological or pathological studies. Search was confined almost
entirely to soldiers, few cases of fever among the civil population being procurable by us for study.
The barracks at Wilberforce and Tower Hill afforded excellent fields for investigation. It should
be noted that the men in these barracks belonged to West India regiments — that is, were natives
of the West Indies who had been serving in Sierra Leone only for a short period.

The troops at Wilberforce had arrived there some months previously from a very malarious
part of the colony, and continued to suffer severely from fever. They numbered about 320 men.
We were informed that out of these no less than 195 men had come to hospital for fever in one
month (July) ; although, as most of the men were not ill enough for admission, the " admission "
rate was much lower. We examined the blood of a large number of the men, botli in hospital
and out of it, and estimated that the parasites were to be found in about a quarter of them taken
at random. The species found were all of those now recognised in most parts of the world.
H. malaria was the commonest ; but cases of H. vivax and H. pnecox also abounded, being
about equal in number. Cases of double infection were frequently observed. The prevalence of
the disease was at its height at the time of our arrival, although quinine had been and was being
sedulously given both for treatment and prophylaxis ; and it was evident that such a number of
cases could not be attributed alone to relapses, but that fresh infections were occurring at the time.

At Tower Hill there was much less fever. We attempted no estimate of the number of
men in whom parasites could be found. Parasites could, however, be easily detected in the
liospital cases. They belonged almost exclusively to H. pracox ; though two or three cases of
H. malartce and H. vivax were observed.

There were very few cases among the troops on Mount Aureole and Kortright Hill. Of
three cases examined in the hospital on Mount Aureole, one contained H. tnalaria; ; another the
melanin of H, mahirii^ ; while the third was negative on a cursory search.

REPORT OF THE MALARIA EXPEDITION. g

The morphology of these Hsemamoebidce presented no differences from the accepted
standards. One of us has been inclined to admit two varieties of H. vivax, one with fine light
brown pigment, and one witli fine black pigment. Both were observed in Freetown ; but the
latter only in one case.

We were much struck bv the absence or paucity of crescents (gametoc\ tes) in cases of
H. prcecox. This fact will be discussed later {^paragraph 19\

We found H. danilewskn of the normal type in a few small birds ; but H. reficta was not
seen by us.

We wished to examine the blood of a large number of the civil population in order to
estimate the percentage of them in which the parasites are to be detected ; but found such an
investigation impracticable.

8. Methods for ascertaining Definitive Hosts.- The long researches of one of us
in India, followed by tliose of Koch, Daniels, and the Italian investigators, have given us a very
exact knowledge of the life-history of tiie Haemamcebidas in gnats, and have shown us how to detect
them in the insects with ease and certainty. It has been noted that in inhospitable species of
gnats the ingested parasites perish within the stomach cavity ; whereas in liospitable species the
zygotes escape from that cavity and develop in the tissues, ultimately giving rise to blasts which
are found in the juices and salivary glands of the insect. Hence to incriminate a given species of
insect with regard to the human Hasmamoebidre, it is necessary only to find the parasites within
that species. In short, the method to be adopted is precisely that used in ascertaining alternative
hosts for any other metoxenous parasite, such as Cestodes and Filaridas, for instance. Care only
is required to determine for certain that the parasites found ui the gnats were derived from human
beings, and not from other vertebrates. It is not necessary actually to infect human beings from
infected gnats, because the general law that infection can be so produced has already been
sufficiently established.

Hence a given species of insect is incriminated simply if we succeed in findino; the
parasites —

(1) in insects bred from the larva and fed on infected persons.

(2) in any insects fed on infected persons — provided that the zygotes found in the insects

are of the proper stage of growth ; or

(3) in a large percentage of insects caught in a chamber where an infected person lives-

provided that the circumstances exclude tlie possibility of the insects having become
ijifected from other vertebrates.

9. Definitive Hosts in Freetown. - Our first object being the search for definitive hosts,
we propose to record our operations in this connection in some detail.

For the reasons given in paragraph 22, suspicion was already strongly excited aijainst all
species of gnats of the genus Anopheles ; and, accordingly, we began by searching for these insects.
Two species were found almost at once, under the following circumstances.

10

REPORT OF THE MALARIA EXPEDITION.

Dr. Berkeley, medical officer of the Lunatic Asylum at the eastern suburb of Kissy,
informed us tiiat there had been a small outbreak of fever among the permanent inmates of that
institution. Tliree persons had been attacked ; one liad died, one had recovered, and one was
convalescent. He was also good enough to bring us a number of gnats which he had cauglit
within the institution. They proved to belong, almost all of them, to Anopheles ; and were of two
species, one a small species which we have named A. funcstus, and the other a larger species called
A. costei/is, Loew. The former were by far the more numerous. [Aeldenfhon /., Plate F.]

The insects brought by Dr. Berkeley were dissected and examined. In one a single
characteristic zygote containing the melanin of H. vivax was found ; and since the melanin of
this species is typical of it, it was scarcely open to doubt that the zygote had been derived from
that human parasite.

No further positive results, however, were obtained from this locality. No fresh cases of
fever occurred, while we failed to find parasites in a large number of the Anopheles subsequently
brought from the asylum. It was, however, interesting to observe these insects in tlie building.
Large numbers of the small species were found gorged with blood and seated asleep in their
characteristic attitude on the walls. They were most numerous on the ground floor and in the
sleeping chamber of the inmates— who were not provided with mosquito nets. Few other gnats
were present.

In the meantime our attention had been called to the fever so prevalent among the troops
at Wilberforce. On searching the barracks and hospital we found a considerable number of the
large variety of Anopheles, namely, A. costalis, already observed in small numbers at Kissy. As at
the asvlum, they were seen gorged and asleep in their characteristic attitude on the walls of the
buildings, especially in dark corners, and were easily captured in test-tubes. Some were so
excessively gorged that they had been evidently willing to fly only to the nearest part of the walls,
just over the bed-heads of the soldiers on whom they had been feeding ; and those which were
at once examined were found to contain human blood — or at least blood microscopically indis-
tinguishable from human blood.

The men of whom about twenty slept without nets in each barrack complained of being
bitten by these insects at night, but added that they were occasionally anno\'ed also during the da\',
especially toward evening. It should be added that no other species of gnat were present within
the barracks. During our stay in Freetown we must have caught or obtained at least two hundred
gnats from these buildings, but only in a single case — a Culcx did the captures prove to be other
than A. costalis. We noted also that there were absolutely no vertebrates other than human beings
within or in proximity to the barracks. Cattle, dogs, cats, bats, monkeys were absent, while,
owing to the buildings having been newly erected, there were not even sparrows, lizards, etc.

The Anopheles caught by us in test-tubes almost all of them females which had evidently
gorged themselves on the men during the preceding night were reserved for microscopical
examination. They were kept alive for 48 hours or more, until their meal of blood had been so
far digested or voided as to permit an easy examination of the tissues of the stomach ; and were
then killed and dissected — the stomach, the thorax, and tlie salivary glands being especially

REPORT OF THE MALARIA EXPEDITION.

11

scrutinized. During our stay, altogether 109 fed female Anopheles cauglit within the Wilberforce
Barracks were examined in this manner.

It has been stated [paragraph 7] that Ha?mamoebid.-e of all three human species iiad been
found in about 25 per cent, of the soldiers at Wilberforce. It was therefore to be expected, if the
Anopheles caught in the barracks were an hospitable species, tliat the parasites should be found also
in a large percentage of these insects. And this proved to be the case. Out of the 109 insects
examined the parasites were detected in 27.

The parasites were in all stages of growth ; from the very youngest zygotes, evidently
derived from the last meal made by the host ; to the mature zygotes derived from previous meals,
and the blasts lying in the salivary glands ready to produce fresh infections of human beings. We
even judged it possible, in some of the dissections, to distinguish the different species of the
parasites by their morphological characters [^paragraph 10]. The following list, giving the serial
number, and results of examinations of each insect in which the parasites were found (the negative
insects being omitted) will be instructive : —

No. 4. Three nearly mature zygotes. Species unknown.

„ 8. One very small zvgote, apparently H. malaria', among stomach cells.

„ 12. Eight nearly mature zygotes. Species unknown.

„ 13. Six mature zygotes. Species unknown.

„ 14. Four very small zygotes, evidently of H. vivax,

„ 17. Several mature zygotes, one containing melanin, probably of H. vivax. Also
empty capsules. Salivary glands loaded with blasts in cells and ducts.

„ 21. Eleven empty capsules (old) attached to stomach. One lialf-grown zygote.
Salivary glands packed with blasts within capsule, cells and ducts.

„ 23, Eight very small zygotes of H. tnalariee.

„ 29. Ten zygotes of H. malaria of 3-4tli day.

„ 31. Several large zygotes.

„ 32. Empty capsules. Blasts in salivary cells and duct.

„ 43. Three very young zj gotes of H. precox.

„ 56. Four young zygotes of H. vivax.

„ 57. Two young zygotes of H. malaria.

„ 61. Several very young zygotes of H. pracox.

„ 62. One medium zygote of H. vivax.

„ 63. Several nearly mature zygotes, probabl)' H. malaria.

„ 65. Several smallish zygotes of H. malaria, and one ver\- young one of H. vivax,

„ 71. Several medium zygotes of H. malaria.

„ 76. One empty capsule. A few blasts in one lobe of gland.

„ 79. One medium zygote with dark pigment.

„ 84. Three mature zygotes.

„ 89. One empty capsule. No blasts found (poor dissection).
„ 91. Six mature zygotes.

12

REPORT OF THE MALARIA EXPEDITION.

No. 92. Very numerous large zygotes, probably H. malaria'.

„ 99. Several empty capsules. Numerous blasts in blood, and a few in cells of salivary

gland none in ducts.
„ 108. One nearly mature zygote.

It is possible that the parasites may have been overlooked in some of the gnats examined.
Tliat a larger percentage of the gnats should not have been infected, and that more zygotes should
not have been found in tliem, was to be expected from the old nature of most of the fever cases
among tlie men S^paragraph 19\ and from the constant use of quinine by the medical officer.

The facts obtained, however, removed all possibility of doubt as to A. costalis being
hospitable to tlie human parasites ; and it was no longer necessar)' to undertake formal feeding
experiments. Indeed the condition of things found in the Wilberforce Barracks amounted to an
experiment of this kind being performed by nature herself under our eyes. This was tlie more
fortunate as we experienced great difficulties in the way of actually feeding gnats on infected
persons in a satisfactory manner. Nevertheless a few such experiments were performed.

On the 17th August, five small Anopheles [A.funestus) caught at Kissy, were fed on a case
containing a few H. malaria. The insects had been naturally fertilized and fed when caught,
but had been kept for some days until they had digested their meal and had laid tlieir eggs. They
were then fed again in test-tubes on the case referred to, and were kept for another two days before
being examined. Two yielded bad dissections, and one died before its meal of blood was digested.
The fourth was negative. The fifth was dissected on the igtli, and was found to contain three
very young zygotes with pigment identical with that of H. malarice.

A few days later, one large Anophele {A. eostalis)^ also cauglit b)' liand and previously
naturally fertilized, fed, and kept in the same manner as the preceding, was re-fed on the same
case. Two da\'s afterwards several young zygotes containing tlie melanin of H. malaria' were
found in it.

In both these successful experiments the insects concerned belonged to large batches of
Anopheles procured from a building where there was no fever ; and numbers of insects of both
batches had been examined and found free from parasites. Judging from this fact, and from the
size of the zygotes found, there could be no doubt that the latter had been derived from the case of
H. malaria". It should be carefully noted, however, tliat both these insects had evidently been
fertilized before they had been caught, and had indeed each laid a batch of eggs before tlie
experiments.

The military medical authorities now put a stop to our feeding any gnats, except those bred
from tlie larva, on their cases. As it took us some weeks to obtain Anopheles in tliis manner, and
as we could then only feed tlie insects in a very unnatural manner, that is, in tubes, oiu" experi-
ments in this line were practically arrested.

Altogether eighteen Anopheles, mostly of the large variety, all of them bred from the larva,
and some of them bred from the eggs of Anopheles caught at Wilberforce, were applied in test-tubes
to the skin of patients containing a few H. prcecox (crescents) and H, malaria, and taking quinine —
no better cases being available. Being isolated in test-tubes when fed, none of these insects

REPORT OF THE MALARIA EXPEDITION. I3

were fertilized, while they could not be induced to feed copiously. AH proved negative as regards
the parasites. As, however, it was already certain that all the insects belonged to hospitable
species, this result was interesting as tending to show that cultivation cxpcrimcnti may fail if not
performed under natural conditions. Tlie subject is discussed later [^paragraph 20\

After our departure, Dr. Fielding-Ould examined numerous Anopheles caught at Wilbcr-
force, and in the houses of natives suffering from fever, and found the parasites in 18 %. His
observations on Culex were negative.

We made no observations oJi Culex or other insects.

We conclude that both Anopheles costalis and Anopheles funestus are liospitable to the human
Ha;mamoebidae. We think that A. costalis is hospitable to all three of the human species ; and
A. funestus certainly to H. malarit^^ and probably to H. vivax. But we made no observations
regarding the connection of the latter with H. precox.

10. The Haemamoebidae in the Definitive Hosts. — The stages of the human parasites
in Anopheles are essentially the same as those of H. relicta, first described by one of us in a gnat
of the Culex pipiens type — a fact already recorded by Koch and the Italian observers. In Plates I.,
II., and III. we give a series of photographs of all these Ha-mamoebidie in the gnat.

The following small differences between the liuman species and H. relicta were noted
by us : —

(i.) Tlie capsule of the zygotes of the human species is somewhat thinner; so that the
y oungest zygotes are more difficult to detect, and sometimes rupture under pressure
of the cover-glass — a thing which rarely happens in H. relicta.

(2.) The mature zygotes seem to contain more blasts than do those of H. relicta.

(3.) The melanin appears to remain longer in the human species.

(4.) The blasts are shorter and thicker, and less bent and twisted, than those of H. relicta —

but differences in the strengths of the salt solutions used may account for this.
(5.) In the human species the blasts tend to lie in the salivary cells in bundles, like bundles
of faggots, and not irregularly like those of H. relicta— least this was very
noticeable in two of the gnats, numbers i 7 and 99.
(6.) Owing to tlie dilatation of the proximal ends of the salivary ducts in Anopheles, the

blasts can be more easily distinguished within these chaiuiels.
It is important to note that, though elements like those provisionally called " black spores "
by one of us were frequently seen in the Freetown Anopheles, they were never detected within the
capsule of the z)'gotes {^paragraph 24\

The )'oung zygotes of H. vivax were alwa) s immediately recognisable b\' the numerous
minute granules of light brown melanin which they contained. The youngest z\ g()tes were, in
fact, almost identical in appearance with the mature gametocytes in the human blood. As the
parasites advance in growth, the melanin seems to decrease in quantity and become sligiitly paler ;
but it was sometimes still to be found even in the most mature zygotes— which, moreover, were
of very large size, and contained very numerous blasts.

REPORT OF THE MALARIA EXPEDITION.

The zygotes of the other two species contained fewer and much darker granules. In the
youngest ones we considered we could distinguish between the melanin of H. malar'ice and
that of H. pr<ecox ; the former possessing large and small granules of a dark brown colour, mixed
togetlier ; tlie latter possessing only large black granules.

Our studies were not sufficiently exhaustive to enable us to speak regarding other differ-
ences noted by the Italian observers. Nor had we time to examine cytological details ~a
tiling to be regretted, because the Romanowsky method does not seem to have \'et been correctly
applied to the study of the nuclear changes in tiie zygotes. We easily noted, however, the
structures first described in H, rel'icta ; namely, tlie alveolar, vacuolated appearance of the z\'gotes ;
the denser chromatoid granules; the division of the parasites into 8 — 12 meres, giving rise to
spherical blastophores carrying blasts in a manner recalling spermatogenesis ; and the minute
spherical enlargements often attached to the immature blasts. We observed also tliat in the
human species, as (to a less degree) in H. rc/iita, zygotes wliicli are little more than lialf grown,
often contain apparently mature blasts.

In several insects many full-sized zygotes appeared not to have ripened —that is, did not
contain blasts ; although others containing blasts were found associated witli tliem.

( ^5 )

IV. BIONOMICS OF THE CULICID.E IN FREETOWN.

II. Differences between Culex and Anopheles. — Our next duty was to study the
habits of the inculpated Anophela with reference to the prevention of gnat-fever. We propose to
give our bionomical observations here,* and to reserve a description of the insects themselves for
the Addenda.

In view of the particular connection which seems to exist between Anopheles and gnat-
fever, it is important to possess information sufficiently simple to enable anyone to distinguish
between them and the common gnats of genus Culex. Such points of difference have already
been recorded by one of us as the result of his observations in India [14] ; and we were able to
assure ourselves that the same differences hold also in Freetown.

(i). Adults. — The principal zoological dis-
tinction between Anopheles and Culex is that the
palpi of the female are long in the former and short
in the latter. But this is of little assistance to those
who are not entomologists, and who may not know
what the palpi are. Fortunately there is a more
striking difference — one which can be perceived by
anyone at a glance — in the attitude adopted by the
respective insects when seated on a wall. In

3. Anopheles and Culex.

Anopheles the axis of the body is almost vertical to

the wall ; in Culex it is parallel to the wall. Popularly put, the Anopheles may be said to stand
on its head, with the point of its tail projecting outward ; while the tail of Culex points downward,
or even a little toward the wall.

Another noteworthy point of difference is the general shape of the body. In Anopheles the
head and thorax are comparatively small, while the long palpi are held in contact with the
proboscis. This gives the insect a peculiarly elegant fusiform shape — like that of a humming-bird
moth ; while the proboscis looks like a long thick beak. On the other hand, Culex has a thick
ungainly thorax, and a thin bare proboscis. In short, the appearance of Anopheles suggests that it
can fly further and more rapidly than Culex.

Thirdly, the wings of Anopheles are generally spotted along the anterior edge (to use popular

* It should be clearly understood that our remarks apply only to our own observations. We cannot answer for facts
in other localities,

i6

REPORT OF THE MALARIA EXPEDITION.

language), while those of Culex are generally plain. There are exceptions to both these
statements ; but the rule holds good in Freetown, and also, according to the observations of one of
us, in India.

The eggs of Amphda have a peculiar boat-like shape, while those of Culex are oval or
lanceolar.

(2.) Larvte. — Here too, very fortunateh', there is a marked difference. The trachea: of
Culex terminate in a long buoy-like breathing tube which projects, sometimes to a great length,
above the tail fins. On the other hand, the tracheas of Anopheles merel)' terminate just above the
tail fins, in two apertures which are nearly flush with the back.

Apparently owing to these facts, the attitude also of the larvae of the two genera is
different : those of Culex^ when at rest, hang suspended head downwards by the attachment of
their breathing tube to tlie surface of the water ; those of Anopheles float flat on the surface like
sticks.

When disturbed, Culex larvne immediatelv leave the surface and wriggle to tlie bottom of
the water, floating up again a few moments afterwards by the buoyancy of their air-tube. The
movements of Anopheles larvae are quite different. They move on the surface of the water with a
few peculiar backward jerks, followed by a pause ; and sink to the bottom onlv when much
molested.

Lastlv, Culex larvae live mostly in artificial collections of water, while Anopheles larvae
prefer natural collections -a point, however, which requires special consideration.

12. Breeding Places of Culex. ^ Freetown, as in all collections of houses, there are
to be found in the vicinity of human dwellings innumerable tubs, pots, shards, etc., in which a
little rain water or household slop water collects. In almost all such in Freetown — tubs, pots,
buckets, cisterns, empty oil-tins, biscuit-tins, sardine-tins, gourds, flower-pots, broken pottery,
crockery, and bottles, even in unbroken bottles thrown uncorked on heaps of refuse — we found
Culex larvje. The only condition necessary to their existence appeared to be an ounce or more of
water preserved from desiccation or leakage. Occasionally, also, the larvae were found in hollows
in rocks, pools by the side of roads, and even in small runnels of water. Very numerous larva? of
a gnat of the C. ta;niatus type were observed in hollows in rocks on the top of Signal Hill (400
feet), near the Signal Station (occupied) ; also some of the same larvae, in a hole in rock hundreds
of vards from human habitations.

Similar facts have been always observed by one of us in India. Drains, ditches, and small
ponds must be added to the liaunts of Culex larva? ; but, as a rule, vessels of water near houses
appear to be their favourite liabitations.

13. Breeding Places of Anopheles. Wc made a very elaborate searcli in Freetown
for Anopheles larva-. Every part of the town shown in a map which was given to us was carefully
examined ; and wherever a breeding place of Anopheles was observed it was entered on the map
[Map II.].

REPORT OF THE MALARIA EXPEDITION.

17

We recorded the following observations : —

(I.) Anopheles larvs were never found in vessels of water, except in a single instance— a tub.

(2.) A mangrove swamp fringing a part of the coast (Aberdeen Creek), far from human
habitations, contained no larvae, although there were numerous fresh-water pools on the edge of
the dry land. Small fish abounded in the swamp.

(3.) Part of a large swamp below Wilberforce Hill, and also one at Kissy, was examined
by ourselves, assisted by ^several natives. Water lay to tlie depth of an incli or two between
clumps of grass, on a basis of flat rocks. Habitations were distant. No larva- found.

(4.) Owing to the hilly nature of Freetown there are not many ponds or large pools. Such
as there are contained no larvae— although in several of them there were no fish.

(5.) Rapid streams contained no larvae.

(6.) Pools left drying after rain in watercourses, or other positions liable to scouring by
heavy rain, seldom contained larvae- at least at the season when we were at Freetown.

(7.) Shallow puddles of rain-water, apt to dry up between the showers, seldom contained

larvae.

(8.) Puddles which lasted from shower to shower, but which were not liable to be scour ?d
out by heavy rain, generally contained them.

(9.) Pools on soil or rock fed by water oozing from the ground, and small slow runnels of
water amongst herbage, usually contained large numbers of larvae — unless liable to scouring.

Altogether we counted within the
area of the map about one hundred prin-
cipal pools containing Anopheles larvae.

Generally speaking, we found the
larvae in small permanent pools not liable to
scouring. We did not find them in vessels,
evanescent pools, pools liable to scouring, large
collections of water, and running streatns.

It would appear, then, that the
larvae require certain conditions, namely,
security from (i) desiccation, (2) scouring.
To these should perhaps be added (3)

security from small fish. 4. a larye Anopheh-s pool In roailsi.le ditch.

As may be surmised, then. Anopheles pools were not found on sloping ground where puddles
either dry up very quickly or are apt to be scoured out by heavy sliowers. On the other hand
they were frequently found on level ground. We did not find tliem on the liills surrounding
Freetown (though they were probably present in a few places) ; we did find them frequently in
the flattest and lowest parts of the town.

The majority of the Anopheles pools were found in the ditches b)' the side of roads and in
certain localities where many small streamlets ooze from the bases of the hills after rain. Others
existed in the course of the newly-made railway. Few were obser\ ed in the vards and gardens of
liouses.

i8

REPORT OF THE MALARIA EXPEDITION.

Most of them contained
green water-weeds, and many
tadpoles and frogs ; but none
contained fish.

In size they varied from
a few square inches in area to
several square yards.

It is important to note
that in no case did we find
Anopheles larva- in pools which,
though otherwise suitable for
them, were distant from human
habitations. We must add,
however, that we did not ex-
amine many such, except in

Lnrs^e An.pln-h. pool produce,! by rniUvny embankment. ^^^^ swampS referred tO above.

In considering these facts it is necessary to remember two things. F'lnt^ Freetown is a
hilh' place with a low subsoil water -circumstances which limit the number of surface puddles of
all kinds, and especially of permanent stagnant puddles. Secondly^ when we carried on these
investigations it was the lieight of the rains ; that is, heavy showers usually fell several times a day.
This, in a hilly countr)', must act in opposite wa)'s as regards surface pools. It constantly
replenishes all these pools, but at the same time it constantly scours out those which exist in
watercourses and on sloped surfaces. A different state of things may prevail as the showers
become less frequent toward the end of the rains ; the smaller puddles will then tend to dry up
between the showers, while those formerly subject to scouring may now cease to be so, and may
become habitable for Anopheles larvae. Thus we thought it likely that after the rains they may be
found in the numerous pools which will then be left in the beds of the drying-up watercourses—
where, during the rains, they would be swept away.

Hence it is not advisable to generalize
too much from these observations, regarding
either the frequency of Anopheles puddles in other
places, or even in Freetown at other seasons.
In some places the puddles must be more nume-
rous ; in others less numerous ; while in Free-
town itself their number and position probably
cli inge from season to season.

14. Distribution of Anopheles in
Freetown. Owing to difficulties in the way of
catching gnats in private houses, we could not
make exhaustive studies of the distribution of the
ndults in various parts of the town

6. Collection of small Anopheles pools

The following facts, however, were observed ; -

REPORT OF THE MALARIA EXPEDITION.

19

(i.) A. costalis was found all over the low-lying areas examined h\ us. That is, the larv;c
wliich yielded this species were found in all these areas ; though it was much more difficult to
obtain the adults. The adults were most numerous in the Wilberforce Barracks (600 feet) ; but
were also obtained in other parts of the town, as far east as the suburb of Kiss)-. No adults were
ever seen in the barracks and officers' quarters on Tower Hill (400 feet) ; although there were
numerous breeding-pools only 500 yards to windward. None were found in the barracks on
Mount Aureole (900 feet) ; although pools lay all round the base of the hill.

(2.) A. funcitui was restricted entirely to the eastern part of the town ; we never found a
larva nor an adult of this species west of Government House. Not one was seen in Wilberforce
Barracks, where A. costalis was so common. Individuals were caught in a house in the town
where some cases of fever had occurred ; at Leicester, a village high among the hills ; and at
some other points. The larva; were common in pools in the eastern quarters, at Kiss}', and otiier
spots.

It is curious that while only the large species occurred at Wilberforce, it was alwost
entirely the small species which was found at Kissy.

15. Bionomics of Anopheles Larvae. We made the following observatit)ns :

(i.) Eggs.— These are boat-shaped, like those oi Anopheles observed in India. The)' appear
to be laid singly on water ; but cohere by their ends, forming typical triangular patterns ; and also
adhere to floating objects, the sides of the vessel, etc. We observed no facts indicating that they
are ever laid on solid surfaces. In vitro the\' take about 24 hours to hatch ; but the period is
probably mucli shorter in puddles.

(2.) Duration of larval stage r- This depends on temperature and amount of food. Under
natural conditions it may probabh' be only three or four days ; but under unfavourable conditions
(cold, overcrowding, absence of food) it may certainh' extend to weeks.* There are reay)ns for
thinking that development is much hastened b\' bright weather, in order to enable the imago to
hatch out before desiccation of the containing puddle.

(3.) Food. — The larv;c were frequently watched floating on the surface and feeding on
filaments of water-weed — amongst which thev often entangle themselves. On dissection, the
intestine was found crammed with these filaments. It was observed that hi vitro the larvas
scarcely grow in size unless they are given large quantities of water-weed- - which they dispose of
very rapidly. On the other hand, larvae were often caught in puddles in which no green
vegetation could be seen. They may eat otiier food, but it would seem as if water-weeds
constitute their favourite diet. It was also noted that the\' obtain shelter among these weeds from
tlie current running tln'ough the pools during or after rain.

(4.) Enemies. — No observations could be made under this head ; but we often found many
trogs and tadpoles in the breeding-pools, apparentl)' living at peace with the lar\ ;f.

(5O Elf'^<:t^ of desiccation. — During most of our stay in Freetown heav}- showers fell several

One of us kept Culcx larva; alive tor tuo months in a bottle in the cohl weatiier in India.

20

REPORT OF THE MALARIA EXPEDITION.

times a day, so tliat the larv;e ccnikl live secure from desiccation in all but the most evanescent
puddles. In September, however, there was a complete break in the rains, lasting three dnys. A
large number ot tiie pools, even many of those containing water-weed, and those fed b)- springs
during rain, dried up completeh'. The question whether the larvat- had the power of living in
t)ie mud at tlie bottom of the pools could now be tested by direct observation. The break in the
rains was followed by heavy showers, which immediately refilled all the puddles. Had the larvie
continued to exist in the mud, tlie\- would now have emerged again. As regards the puddles in
which the mud had completeh' dried, this was not the case. No larv;e at all were found in them
for at least two days after the rain had refilled them. After that interval larv;e again appeared ;
but they were very small ones, evidently just hatched from the egg. On the other hand, it was
frequently observed that if the mud did not become completely dr\', the larva; would emerge into
active existence after another shower. These observations were supported by some experiments
/;/ vitro ; and we therefore conclude that the larv;e can withstand partial, though not complete,
desiccation,*

(6.) T/ir sauir puddles constantly occupied. -- ha\'e suggested [paragraph 13] that the
position of the breeding pools may change according to the seasons ; but while we were in
Freetown there was no change of season, and we generalh' found Anopheles larva; in the same
puddles- namel)', in those which were suitable for them. Thus, of two puddles lying close
together, one would never contain larvae, and the other would alwa\'s contain tliem. The
explanation of this probably is that the larva- perish in tlie unsuitable pools, or that the adults
generally return to the same pools in order to la)- their eggs. It seems likely that the adults
generally lay their eggs in the pools in which the)- themselves were bred ; and tliat the insects
thus learn by experience the places most suitable for them.

(/.) Detection. -It is easy to overlook Anopheles larviK unless the}- are searched for in a
bright light.

(8.) Pnpa\ Tlie pupa- of Anopheles seem to be smaller than those of the commoner
species of Ciilex. The\' require about 48 hours to reach maturit\' /// vitro ; perhaps less in natural
conditions.

16. Bionomics of Adult Anopheles, (i.) Hatching. -The adults generally hatch out
in the evem'ng ; but their exit seems often to depend on the meteorological conditions ot the
moment, and appears to be dela) ed by rain\- and wind)' weather.

(2.) Food. The\ can easily be kept alive in glass cages, test-tubes, bottles, etc. We kept
some in this manner for a fortm'ght, and could doubtless have kept them longer if we had wished
to do so. We were able to confirm Bancroft's statement [18] that gnats feed on bananas; but
they seem to prefer the fresh fruit. During the day the insects remained at rest on the walls of
the cage ; but in the evening began to fly about and to walk over the fruit, plunging their
proboscis into it in man) places, so that the banana was sometimes covered with the gnats, both

' One of lis rearcil adults from fiill-grnwii l:\rvm kept on ilnnip blotting-paper (in India) ; but found that tlie )inini; larvic
died u hen kept umler tlicsc conditions.

REPORT OF THE MALARIA EXPEDITION.

21

male and female. They also drink water frequently, and can often be seen to be distended with
the fluid. Raw meat was offered to them, but they could not be observed to touch it. Earth
placed at the bottom of the cage seems to be suitable for them.

According to the accounts of the soldiers at Wilberforce, they bite almo;>t entirely in tlie
evening and night, but have been known to feed on men during the da\'. 'riic\- can certainh- be
fed on men artificially during the daytime, simply by placing them in test-tubes and then applying
the mouth of the tube to the skin. The stomach can be observed to become distended in from
one to two minutes or more ; after which the insect continues to suck, but commences to
evacuate by the anus serum containing a small percentage of red corpuscles. Culex voids only a
clear fluid under the same circumstances. The insects sometimes continue sucking like leeches
for five or ten minutes, voiding blood all the while ; but at otlier times soon withdraw the
proboscis and then try another spot. It was noted, liowever, that Anophclfs fed in this manner,
even after they had remained sucking for five or ten minutes, never showed any great distension
of the abdomen ; while the contents of the stomach still remained for some time transparent and
red as seen through the scales of the living insect. Moreover, in these cases the meal was
generally digested or voided within about 24 hours.

On the other hand, Anopheles which had fed themselves under natural conditions generally
presented a very different appearance. They were enormously distended ; while the contents of
the stomach were thick, opaque, and black, and sometimes did not disappear for three da)'s. Tlic
only inference is that, under natural conditions, the insects which can manage to do so gorge
themselves over and over again during the night — probably from the same subject.

(3.) Propagation. — We also observed tliat while naturall3--fed gnats invariably laid eggs
after two or three days, those which had been bred from the larvas in captivity, and had then been
isolated and fed in test-tubes, never did so, altliough before being isolated they had long been in
company with males. Tlie inference is that fertilization takes place only after the female has
been fed.

We noted also that, in a cage where many male and female gnats, both Culex and
Anopheles^ were kept together for weeks, eggs were never laid -although the insects were fed as
described on bananas, and the cage contained water for them to lay their eggs in. It seems, then,
that a meal of blood is necessar)' before fertilization.

Lastly, we observed that previoush' fed and fertilized insects would lay a second batch of
eggs after a second meal of blood, without a second fertilization ; but never laid a second batch of
eggs without a second meal of blood. That is, one fertilization suffices for several batches of eggs,
but one meal of blood for only one batch of eggs.

1 hese observations are wholly in accord with the results of the prolonged ■study of many
kinds of gnats made in India by one of us ; and it therefore seems likely that the following law is
likely to liold good for the CuUcidce which feed on men - at least for the commoner species :

Although tliese gnats can live indefinitely on fruit and perhaps juices of plants, the female
requires a meal of blood, both for fertilization and for the development of her ova. In other words,
the insects need blood for the propagation of their species.

22

REPORT OF THE MALARIA EXPEDITION.

Blood was never found in male Culidda; in Freetown- according with the general law.

(4.) Haunts.- '"The large majority of Anopheles cauglit by us in dwellings were females
wliich were generally much gorged, and, if fed at all, were invariably fertilized ; in other words,
the males and unfed, or only slightly fed, females did not generall)' remain in the houses during
tlie daytime, or if they did remain, kept in the roofs or other dark places where they were little
observed. On the whole, wc tliink that only those females which are so gorged tliat thev cannot
fl\' far remain in tlie houses during the da^'. We observed that if a cage full of Anopheles was
disturbed in tlie daytime, the insects always struggled toward the liglit as if to fiv out from tlie
windows ; and several whicli escaped from the cages actually did so. On one occasion a large
number escaped from their cage during tlie night in the rooms occupied b\' one of us none of
tlicm could be seen next morning.

Yet we may be quite sure tliat botii the males and the unfed females haunt the houses
during the night. The invariably fertilized condition of tiie gorged females cauglit in the houses
shows that the males must be present in the houses when the females feed — since the latter are
often so much distended after feeding that they are obviously unwilling to fly even a few feet from
tlie bed of their victim ; in other words, fertilization must take place within the houses. The
unfed females must, of course, resort to human habitations during the night in order to obtain their
ft)od at all.

These facts would seem to indicate that in Freetown, in tiie rainy season, the Anopheles
resort to the houses during the night, but that all except the gorged females live elsewhere during
the daytime — possibly sleep in the trees and shrubs. The point is of interest as tending to show
that large numbers of Anopheles may be present in a dwelling during the night, without it being
easy to find them during the day.

It should, however, be added, that in India males and unfed females were often found in
the houses in large numbers by one of us. Possibly different species liave different habits in
this respect.

Several old residents of the country informed us tliat gnats arc usually ver)' prevalent in the
presence of much vegetation — especially long grass and undergrowth. Though it is difficult to see
how such can favour the larvae, we can understand that much vegetation can shelter the adults of
certain species, which may even feed on particular kinds of plants when they cannot obtain blood,
and may consequently find it easier to live where these plants afford them both food and shelter
than elsewhere. It must also be remembered that gnats can certainly bite birds and other
mammalia besides man ; and that such are apt to congregate where tliere is mucli vegetation.
On the whole, then, there is nothing improbable in tlie idea that the Freetown Anopheles should
live outside tlie liouses in tlie daytime.

(5.) Proxifn/tY of breeding-pools to houses. The gorged females are, as we observed, alwa\'S
fertilized, and must therefore probably lay their eggs a few days later or perish. We often noticed
that gravid females kept in dry test-tubes made no attempt to lay eggs unless a drop of water was
put in— in which case they often deposited their eggs almost at once in the fluid. These
observations suggest the conclusion that the females must return to water a few days after each

REPORT OF THE MALARIA EXPEDITION.

23

meal of blood. As Anopheles larvae were not found in vessels of water close to houses, the only
inference which remains seems to be that the pregnant females must return, not to any water, but
to some pool suitable for her oflFspring. If such a pool exists close to the house where she obtained
her meal of blood, her journey need only be a short one ; but if it be at a distance, she must fly
correspondingly far- and may often be obliged to do so against the wind, or through heavy rain,
or between trees.

It is therefore highly probable tliat, unless they can find animals and birds to feed on.
Anopheles must seek their food in houses which are as near as possible to their breeding-pools, and
also, vice versa, select pools for their eggs wliich are as near as possible to the places where they
obtain their food. In other words, they are not likely to neglect adjacent houses and pools in
order to visit more distant ones. Of course many individuals must go astray— must be carried
away by winds and so on ; but it seems reasonable to expect that, as a rule, the breeding-pools and
feeding-grounds will be as close together as possible.

Where necessity compels, however, it is probable that Anopheles do travel considerable
distances to and fro. This must especially be the case during the dry season, when the pools must
be much more rare— -unless we can show that at that time the surviving adults cease to feed at all
and " hibernate."

It is noteworthy that in the Tower Hill barracks we never found Anopheles, although there
were numerous breeding-pools at a distance of only 500 yards, both to leeward and windward.
The barracks are situate on a hill only 400 feet above the sea, and are surrounded by open grass,
over which the insects could fly or be carried by the wind ; though it should be added that
occupied houses intervene between the pools and the barracks. Perhaps the insects arc all
attracted by these houses. The same thing was observed regarding the barracks on Mount
Aureole.

The question as to the maximum distance possible between a house and a breeding-pool
is an important one, but difficult to reply to. The distance will probably depend largely on local
conditions, prevalent winds, screens of trees, presence of other animals, etc. We must remember
that while wind may assist the insects going one way, it may equally oppose their return. On
the whole it appears difficult to imagine tliat this maximum distance can be very great — more
than half a mile, for instance ; and certaini\' we never found Anopheles larva" except in much
closer proximity to houses.

Certainly gnats can visit ships lying fairly close to the shore. Dr. Wigglesworth was kind
enough to give us some gnats which he had caught on board the S.S. Fantee, on the West Coast
of Africa ; and one of these was an Anopheles. But it must be remembered that insects blown
across water are likely to travel much further than on shore — where hills, trees, and houses
intervene to afford them rest and shelter.

If large numbers of Anopheles are found really far from human habitations, it will be not
unreasonable to suppose that they can procure other besides liuman food. Anopheles are known to
feed on horses and cattle, and may possibly bite other mammals, birds, and even reptiles. But it
must be remembered tliat, in towns and villages at least, men are generally the commonest
yertebrates present,

24

REPORT OF THE MALARIA EXPEDITION.

Owing to their habit of breeding in the vessels of water which generally abound near
houses, the pregnant females of Culex need not fly so far to find water suitable for their eggs. It
is possibly owing to this fact that, to judge by their more clumsy shape, they are less adapted for
prolonged flight than Anopheles.

(7.) Not attracted hy lamps. It is often thought that gnats are attracted by lamps and
candles, and perisli in them. Tliey may be attracted to houses by lights burning in the windows;
hilt we have never seen them liovering round the flames as moths and other insects do. Tlicy
>cem to bite less rcadilv when there is a light in the room.

(8.) Act of puncture.- On applying Anopheles in test-tubes to tlie skin we observed that tlie
insects would sometimes make puncture after puncture without drawing any blood. In such cases
however, each puncture was invariably followed by the usual weal — showing that the insect
always commences work by injecting some of its saliva. It therefore follows that an Anopheles may
inject some of its saliva (possibly containing the blasts of the Haemamoebida") almost instantaneously
that is, before tlie victim feels the irritation and drives the insect away.

It is certain that one can be bitten without knowing it — especially during sleep. Thus one
often finds gorged gnats within the mosquito netting in the morning — without having been at all
conscious of their bites during sleep ; and it is therefore probable that those who sleep without
nets may be much bitten without appreciating the fact. Even the weals often disappear in an
iiour or two ; so that not even the marks of the punctures need necessarily remain until next day.

One of us thinks that much less irritation is caused if the insect is allowed to suck its fill,
and has frequently observed the fact on liis own person. This may be due to much of the
irritating saliva having been sucked back during haustellation.

From several accounts it would appear that Anopheles hover over their victim less than Culex
do, and consequently do not attract his attention so much by humming.

People often imagine that gnats will not bite tliem ; but it seems to us impossible to accept
such statements without sufllicient experimental proof. What is more likely to be the case is that
some persons do not much feel the punctures. The skin of some persons is not very sensitive ;
and it is moreover possible that immunity may be acquired against the irritation of the injected
saliva. Thus persons who have recently arrived in the tropics are well known to sufi^er more than
old residents. This does not necessarily mean that the latter are less frequently bitten, but,
possibly, only that they have become comparatively inured to the irritation.*

17. Bionomical Questions still requiring Investigation. — The facts about gnats
hitherto collected by no means exhaust the subject. We will indicate some of the more important
questions which we found it impossible to deal with.

(i.) Life in the eiry season. -Between the rainy seasons man)' places in tlie tropics are
extremely arid and free from pools suitable for Anopheles larvne. How then do the insects m iinge
to continue the species from one rainy season to the other ? We may assume (i) that the larvne

* It is however possible that the body may in the course of time produce some substance offensive to the insects, just as it
may produce substances offensive to micro-organisms.

REPORT OF THE MALARIA EXPEDITION.

25

may continue to exist in such pools as do remain, the insects multiplying enormously after the first
showers ; or (2) that the eggs may lie dormant in mud ; or (3) that the adults may "hibernate,"
or at least live on without feeding on blood at all, and consequently laying no eggs. We cannot
pretend to give an answer to this question. In Italy it appears that the adults hibernate through
the winter. One of us made an observation tending to show that the eggs can withstand
desiccation for several months ; but this requires confirmation. The subject appears to be of great
importance in connection with the prevention of gnat-fever \_paragraph 28\

(2.) Other subjects. — It is necessary also to examine how far Anopheles do or do not exist
apart from human dwellings ; whether they can breed in other collections of water than those
mentioned above, as, for instance, in rain-water collected in leaves ; whether they really have any
connection with rank vegetation ; how far they can spread from their breeding pools, how far they
feed on animals, and so on.

We must again emphasize the fact that our remarks as to the bionomics of these insects are
drawn only from our experiences within a limited area of Freetown \^Map II.] in the months of
August and September. We can make no statements regarding their habits, or the habits of other
species of Jnophe/es, outside this limited area, or at other seasons.

18. Source of the Wilberforce Anopheles. — As an instance of the difficulties which
may be met with, we may mention that, in spite of repeated efforts, we never succeeded in
finding the source of the J. costalis which were so prevalent in the barracks at Wilberforce. These
barracks are situated on a ridge 600 feet above sea level, and are surrounded by native houses and
gardens, and by much rank vegetation. The ground slopes on either side down to the plains.
Far below to the west (that is, to windward during the rains) there are a marsh and a mangrove
swamp.

We searched in vain every spot likely to harbour Anopheles larvae ; and even examined the
distant marsh and mangrove swamp without positive results. After our departure Dr, Fielding-
Ould and Captain Smith, r.a.m.c, continued the search — equally in vain, except that they found
larvae in pools 1,500 yards away {Addendum 11.].

It was often observed, however, that the Anopheles frequented two or tlnee of the barracks
in preference to the other buildings, and that these barracks were at the end of the block of houses.
At the same time, the insects were common in the houses of the officers, who lived at that time in
the village. These facts suggest that their source existed near these buildings, and not at any
great distance, and that it was probably overlooked owing to the thick vegetation present. It
seems very unlikely that such numbers of the insects could come from breeding pools in the
marshes which lie thousands of yards away in the plain below.

The fact that so many of them were caught for examination seemed materiallv to affect
their numbers ; but we noted that newly-arrived insects invaded the barracks on one, if not more,
occasions.

P

(26)

V. DISCUSSIONS.

19. Questions regarding the Parasites. — Having recorded our observations in Free-
town, we propose next to consider some questions of importance in connection with our subject.

The life-history of the Hsmamcebidas as now known, and as given in the terminology
previously adopted by one of us in consultation with Professor Herdman [15], is as follows
[Plates /., //., ///., //^.] :-~

The youngest parasites exist as aincebula or tnyxopods within the red blood-corpuscles
of the vertebrate hosts. On reaching maturity they become either sporocytt's, or gametocytes.

The sporocytes are destined for the asexual propagation of the organisms within the
vertebrate hosts. They give rise by division to spores ; which escape into the plasma, enter
fresh corpuscles, and in their turn become amoebula? — thus continuing the species indefinitely
in the blood.

The gametocytes, however, are sexual forms, male and female- the male containing
a number of microgametes ; tiie female, one macrogametf. They remain unchanged within the
vertebrate hosts ; but on being drawn into the stomach of a suctorial insect, perform their
sexual function. The male gametocyte emits its microgametes ; one of which enters a macro-
gamete and fertilizes it. The fertilized macrogamete is called a zygote.

If the suctorial insect be a species hospitable to the parasite, the zygote next escapes
from the contents of the stomach, pierces the wall of the organ, and affixes itself in or on
the outer coat. Here it grows largely in bulk. Its substance divides into from about eight
to twelve meres. Each mere becomes a hlastophore bearing a large number of filamentous
blasts affixed to its surface bv one extremity. As growth advances the blastophores disappear,
leavin<2; the capsule of the zygote packed with the blasts. The capsule now ruptures, allowing
the blasts to escape into the body-cavity of the insect. From this they work their way into
the insect's salivary gland ; and finally pass from this gland into the blood of a new vertebrate
host, in which they eventually become the amoebulae with whicli the cycle commenced.

As to terminology — it will be perceived that we use the word "spore" for the asexually-
produced progeny of the parasites, and the word "blast" for their sexually-produced progeny.
Originally, however, neither word possesses such restricted meanings: a "spore" is a single cell
capable of separating from the parent and of starting by itself a new bion or individual ; while
"blast" simply means a bud. Considering, however, that the recent demonstration of typical
sexual functions among the Coccidiidae and Ha?mamoebidae originates the new case of such
functions (apart from simple conjugation) among unicellular animals, it may be now justifiable

REPORT OF THE MALARIA EXPEDITION.

27

to employ these terms as indicated. We may admit that, strictly speaking, the blasts are also
spores, while the spores are, in a sense, also blasts ; but it will certainly be convenient in the
present case to apply the word spore only to the asexually-produced progeny, and the word
blast only to the sexually-produced progeny.

Obviously the zygote is the homologue of a fertilized ovum ; and the blasts are iiomo-
logues of the cells which spring from the fertilized ovum, and wliicii construct tlic tissues ot
multicellular organisms. Only, in this case the blasts give rise, not to a cluster of colls, but
to a cluster of distinct unicellular animals — by a kind of polyembryony in fact. Hence the
use of the word "blast" for the progeny of the zygote appears to derive sanction from the liomo-
logous use of the same word in embryology. The word "zygote" seems to be acquiring the
restricted meaning of the result of union of two similar gametes ; we use it as often applied,
namely, to express the result of union of any two gametes.

Of course otlier terminologies may be preferred by some. Professor Ray Lankester lias
recently been kind enough to suggest terms, which bear the weight of his authority and maj'
be liked by many. He suggests " androspore " and " gynospore " for microgamete and
macrogamete respectively — terms certainly much more definite ; " gametospore " for zygote ;
" nomospore " for tlie asexualh'-produced spore ; " oudeterospore " for any spore which is not
differentiated so as to be male or female ; and " gametoklasts " or " gametoblasts," or even simply
" filiform young," for the blasts.

Manson was the first to interpret rightly the ascertained facts about the sexual propagation
of the parasites, and his views have been adopted by other writers ; but lie has attempted no
terminology. Grassi and Dionisi use " gamete," " microgametogene " (for microgametoc^ te),
and zygote [19]. The term gamete had been previously applied by Sciiaudinn and Siedlecki to
the case of some of tiie Coccidiidae. The Italian observers also use the word " sporozooids "
for the blasts.

Koch employs simply "spermatozoon" for microgamete [11]. The Z)'gotes lie calls
"spherical bodies (Kugelformige Gebilde) " ; the meres, " secondar)- spheres"; and the blasts,
" sickle-shaped bodies (Sickelkeime)."

The terms " sporozooid " and " sickle-sliaped bod\- " suggest somewhat doubtful analogies
with the Coccidiidae. The former term, moreover, is not very intelligible — sporozooids being, in
fact, spores ; while the so-called spores of the sporozoa are really often sporocysts. Compare also
Mesnil [20].

The simple expressions ovum and sperm ma\ be preferred b\- man)' to macrogamete and
microgamete. Professor Harvey Gibson suggests " oosperm " that is, the combined ovum and
sperm — for z}'gote. The word " zooid " has been suggested in the place of blast ; but zooid has
the acquired meaning of a motile cell, and we do not yet know that the blasts arc motile.

A biological point of some interest requires reference. Several writers seem to assume that
the zygote in the gnat is the same individual organism as the female gametocyte in the vertebrate
host — that it is, in short, the fertilized female parasite. This idea receives some support from the
fact that the zygote contains the melanin of the gametocyte. On consideration, however, it

REPORT OF THE MALARIA EXPEDITION.

seems much more likely that the life of the individual gametocytes, both male and female, ceases
with the sexual function in the cavity of the insect's stomach, and that at that moment the life of a
new bion — the zygote- -begins. The gametocyte and the macrogamete are not identical. The
former contains the latter. Perhaps this fact is best indicated by the presence of those minute
spherical appendages, which have long been observed in connection with the parasites after they
escape from the enclosing corpuscle, and which Professor Herdman suggests may be the
liomologues of polar hodies. Thus tlic female gametocyte really contains several cells, only one of
which, however, reaches full development as a macrogamete. Similarly tiie male gametocyte
also contains several cells, only one of wliich becomes mature and gives rise to the microgametes.
Hence it is not tlie female gametocyte, but the progeny of the female gametocyte, which is
fertilized, and this fertilized progeny constitutes a new individual, which passes its existence in
the tissues of the gnat. That the macrogamete retains a portion of the tissues (containing the
melanin) of its parent gametocyte is not inconsistent with biological laws ; but it should be noted
that, according to Mac Galium, the zygote of one avian species of the Hasmamcebidae actually does
discard the melanin of the parent gametocyte.

Hence it would seem that the Hxmamcebidie are organisms which exhibit the phenomenon
of " alternation of generations." Their full life-cycle consists of two stages— one passed principally
in the vertebrate host ; the other entirely in the insect host.

Mannaberg's idea tliat two or more amoebuhe in one corpuscle conjugate, lias found support
from the observations of one of us in comiection witli H. relkta. It seems possible tliat the
gametocytes are produced by such conjugation. At any rate, it is difficult to understand what else
but conjugation can happen to two or more amcebuls in this position.

It is very noteworthy that, while Europeans who come from the West Coast of Africa
suffering from gnat-fever often contain large numbers of crescents, these bodies could scarcely be
found at all in Freetown. This experience tallies with the observation of one of us in very
malarious districts in India [21]. It would seem that gametocytes cease to be produced, at least in
lariie numbers, when an infection has lasted a long time- as for instance more than six months or
a year. This may be explained on the supposition that the number of parasites tends to diminish
as a case advances, owing to gradual production of partial individual immunity, and that it is
therefore rare to find two amoebulje in one corpuscle in old infections. Of course, in very
malarious localities the majority of cases are old infections ; whereas patients who resort to the
Tropical Ward in Liverpool are generally comparatively recent cases [22].

We have used the taxonomical nomenclature previously suggested by one of us [15]. It
is as follows (inclusive only of the parasites of men and birds) :

Family : HitMAMCEBiDvE, Wasielewski.

Genus I. Hcemamoeba, Grassi and Feletti. The mature gametocytes are similar in form
to the mature sporocytes before the spores have been differentiated.

Species l : Hamamceba danUewskii, Grassi and Feletti. Syn. : Laverania danllewskii,
Grassi and Feletti, in part ; Halteridium dani/ewskii, Labbe ; etc. Several
varieties possibly distinct species. Parasite of pigeons, ja) s, crows, etc.

REPORT OF THE MALARIA EXPEDITION. ^9

Species 2 : Hamamaha relicta, Grassi and Feletti. Syn. : Hamamceba relicta + H. mb-

prcecox + H. subimmaculata, Grassi and Feletti ; Proteosoma grassii, Labbc ;

etc. Parasite of sparrows, larks, etc.
Species 3 : H^mamaba malar'ia, Grassi and Feletti. S)'n. : Ha-mama^ba lavcrani,

Labbe, in part. Parasite of quartan fever of man.
Species 4 : Hamamoeba vivax, Grassi and Feletti. S}'n. : Hamamoeba laverani^ Labbe,

in part. Parasite of tertian fever of man.
Genus II. Hcrmomenas^ gen. nov. Syn. : Laverania, in part + I-Le?na>na;b(i, in part,

Grassi and Feletti. The gametocytes have a special form (crescentic).
Species : Hamomenas precox, Grassi and Feletti. Syn. : Hamamoeba prcecox + H.

immaculata + Laverania ynalariee^ Grassi and Feletti ; H^emamceba

laveraniy Labbe, in part ; etc. Several varieties- possibly distinct species.

Parasite of the irregular, remittent, pernicious or aestivo-autumnal fever of

man.

The gametocytes of H. dantlewskii are crescentic, but they are still shaped like the
sporocytes (which are also crescentic) — the shape of both being simply determined by tlie
exigencies of space within the corpuscle. There appears, then, to be no sufficient reason for
separating this species from the others of genus Hiemaniceba, in which the gametocytes and
sporocytes liave the same shape. On the other hand, H^eniomenas preecox is sliarply distinguished
by the gametocytes having a peculiar form of their own. Much confusion has been caused by
the belief of Grassi and Feletti, who first named these organisms with precision, that the
gametocytes of H. prcecox are a separate species, akin to H. danilewskii — both being placed b\'
them in a separate genus, Laverania. This belief they have now abandoned ; and it therefore
seems necessary also to abandon the genus Laverania. Several observers recognise more than one
species in genus Hcemomenas — namely, a tertian, a quotidian, and possibly an unpigmented
quotidian parasite ; but, pending further research, we have accepted only one species — H. prcecox.

The different prevalence of the three human species at different but contiguous spots
(as at Wilberforce and Tower Hill), is hardly consistent with the idea that tliey are merely
interchangeable forms of one species of parasite.

20. Cause of Occasional Failures in Direct Cultivation. — We have noted
[paragraph .9] that a number of Anopheles fed in test-tubes on cases of haemamoebiasis, and not
fertilized, failed to show parasites ; while two Anopheles which were fed in the same manner
but wliich were previously fertilized, did contain them. In this case the failure ma)- be attributed
to tlie fact that the patients contained but few parasites and were taking quinine ; but previously
one of us, in association with Dr. Daniels, obtained negative results with a considerable number
of Anopheles fed in test-tubes oil two excellent cases of crescents in Calcutta. The Italian
observers also note similar failures in gnats known to be hospitable to the parasites. What is the
cause I

Grassi attributes it to immunit)- in certain individual gnats. This can scarcely be the

30

REPORT OF THE MALARIA EXPEDITIOJJ.

true cause, or at least the whole cause — because it sometimes happened in the Indian experiments
that out of a large batch of Culex (according to Giles, C. fatigam [23]) fed on birds with
H. nlicta, every insect would become infected — or almost every insect. It is scarcelv likely that
the eighteen insects we refer to in paragraph 9 were all immune, while 25% of AmphcUs ot the
same species caught at Wilberforce contained parasites.

The explanation which suggests itself is that something was omitted in the experiments,
which is present under natural conditions, and which is essential to the cultivation of the
parasites. What this is we cannot say for certain ; but it is noteworthy that all the successful
experiments made by one of us in India, without exception, were made with insects fed in
mosquito-nets in the presence of males ; while his negative experiments with various species of
Anopheles fed on human subjects were nearly all made with females isolated in test-tubes,
and therefore not fertilized.

Paragraph 16 will suggest the reason wh\- fertilization should affect the question. The
ingested blood is really required for the nutrition of the eggs. If the ova are not fertilized the
blood cannot be much needed by the insect, and is possibly evacuated without some digestive
process which perhaps is necessary to the vitalitv of the zygotes. We know that verv subtle
differences influence the vitality of the zygotes, because otherwise they would not perish in some
species of gnats and live m others.

The point requires careful study, because until it is elucidated negative experiments
cannot be entirely relied on.

The Indian experiments have shown that there is considerable variation in the number
of zygotes found in gnats fed even on the same subject at the same time. This variation
must depend on differences in the quantitv of blood ingested bv different individuals ; and
also possibly on some differences of quality in their digestive juices. But, at the same time, it
was demonstrated tliat few individuals of a liospitable species entirely escape infection if fed
in a natural manner.

21. Known Facts about Malaria Explained.— Caution must always be used before
accepting popular tlieories regarding the diffusion of disease ; but it is remarkable that many
such ideas respecting malaria are explained and justified by the discovery that the disease is
carried by Anopheles. We will briefly indicate the principal points.

(i.) Malaria is endemic. Anopheles are more numerous at some spots tiian at others,
and are entirely absent from manv places.

(2.) Swampy ground favours malaria. -Anopheles breed in surface puddles.

(j.) Level ground favours malaria.- Pooh suitable for Anopheles must be more common
on level than on sloping ground, e.g., on plains and in valleys, than on mountain sides.

(4.) Rain favours malaria. -Anopheles pools largeh' depend on rainfall.

(5.) Malaria is connected with decaying rock. — Anopheles may breed in hollows in rocks.

(6.) Malaria often occurs when the soil is disturbed. — Digging must often result in the
formation of puddles suitable for Anopheles.

REPORT OF THE MALARIA EXPEDITION.

31

(7.) Embankments favour malaria. — They also favour the formation of surface puddles.

(8.) Towns are Inimical to malaria. — Stagnant surface puddles are not likely to be as
numerous in crowded, well-drained cities, as in rural areas.

(9.) Cultivation and surface drainage tend to remove malaria.-- They also tend to remove
waste water suitable for Anopheles and lying on the ground.

(10.) Malaria is not particularly; connected with large bodies of water. Gnats do not often
breed in such.

(11.) Malaria occurs on ships. — Gnats, including Anopheles., visit ships.

(12.) It is particularly dangerous to sleep in malarious places, especially at night. — Gnats easily
bite sleeping persons, and usually feed at night.

(13.) Ground floors are most dangerous.- Gnats seem to remain near the ground.

(14.) Mosquito-nets protect from malaria. — They protect also from gnats.

(15.) Warmth favours malaria. — It favours also gnats, and the Haemamoebidas within them.

In the remarkable work [i] which seems to be the first published exposition of the gnat-
theory of malaria. King suggested many of these striking analogies — and indeed based his theory
on them. Laveran, Manson, Bignami, and others have also independently entertained the same
ideas— which may well occur to anyone who considers the subject at all. But it is now necessary
to make an important correction in these views. King — and indeed other observers -seems to
have thought that all gnats rise from swamps. A close student of the bionomics of gnats,
however, might have almost shattered the whole argument at the outset by remarking that many
of the commonest gnats do not rise from swamps at all, but from tubs, pots, etc., in the vicinity of
houses ; and are indeed most prevalent in the heart of large cities and in other places where there
is little or no malaria. It is clear, then, that King's arguments can apply only to certain species of
Culicidre, namely, those which breed only in pools on the ground.

King also employs other analogies which seem to be less sound. Accepting the popular
views, he considers that both malaria and gnats can be blown long distances, as to the summits of
hills. It is probable that in many such cases the gnats really breed close at hand ; though the
observer, under the influence of the popular superstition, prefers to think that his malaria comes
from the nearest marsh, although that marsh mav be miles distant. King also suggests that white
men are more susceptible than black men, because gnats can see the former more easily. As a
matter of fact, it is always observed that gnats prefer to settle on dark surfaces ; while the
susceptibility of white men is more probably due to comparative absence of immunity than to
more frequent infection.

22. Are other Insects besides Anopheles hospitable to the Human Haema-
mcebidae? — Returning to the subject just touched upon, it will be readily perceived that out of
the fifteen analogies given in the last paragraph, no less than nine (the first nine) can apply only
to insects which breed in pools of water on the ground. For instance, they will not apply to
species of gnats which usually breed in vessels of water. Such gnats cannot be said to have a
localized distribution, because they are to be found in the neighbourhood of almost every dwelling

32

REPORT OF THE MALARIA EXPEDITION.

in the tropics. They have no particular connection with swampy ground, level ground, or
decaying rock. They are not particularly encouraged by rain, by digging, or by embankments.
They are not removed by cultivation or surface drainage ; while they swarm in cities. Hence
we may almost venture to aver that if pot-breeding gnats could carry malarial fever, almost all the
phenomena of the distribution of the disease would be different from what they are known to be.
That is, the disease would be most prevalent in cities ; would have no particular connection with
marshes and level ground, or decaying rock, or rain, excavations, or embankments ; and would
certainly not be removable by surface drainage. In short, it would certainly be present where it
is not present, and absent where it is not absent.

It will be seen from Section IV. that these considerations would seem to exculpate a large
number of species of Culex which frequently, if not always, breed in vessels of water.

Thev would also exclude most other suctorial insects, such as fleas, bugs, lice, etc.

They would not, however, exclude other suctorial insects which, like Anopheles, breed
exclusively or almost exclusively in pools of water. It is impossible, without more study, to say
how manv such insects exist. Certainly some species, even of Culex, can often breed in pools
of water.

The Indian observations ' with "grey mosquitoes" [Culex p'lpiem type) and "brindled
mosquitoes" {Culex taniatus type) all proved negative with the human parasite — with the doubtful
exception of one individual. The experiments were very numerous, and the feeding was done
under natural conditions in mosquito nets [paragraph 20].

The Italian observers record negative results with Italian Culex.

Koch, however, thinks that Culex may possibly be involved [ii].

On the other hand, some nine species of Jnopheles, existing in widely separate parts of the
world, have already been incriminated.

To sum up, while it seems improbable, or indeed very improbable, that the common pot-
breeding species of Culex are involved, it is scarcely safe as yet to exculpate the genus entirely.
Observations regarding other gnats and insects which breed in puddles are still required. But on
the whole it appears more probable that only gnats of the genus Jnopheles are concerned in the
propagation of liuman malaria.

23. Are other Vertebrates besides Man hospitable to the Human Haemamoe-
bidae ? Dionisi records [24] that the two species of parasites found by him in bats are
morphologically very similar to H. pr^ecox and H. malaria ; and Koch says [11] that the parasite
found by him in monkeys is like H. vivax. These parasites may perhaps be identical with the
lumian species.

The parasites of birds can scarcely be communicable to man, being too dissimilar to the
human ones. Exhaustive search in the blood of other mammals besides bats and monkeys is still
required. In many places dogs are popularly supposed to get malarial fever.

The Indian experiments showed that H. relicta of sparrows can be conveyed by C. fatigans
to crows and weaver-birds. Reasoning from analogy, then, we may suppose that the human

REPORT OF THE MALARIA EXPEDITION.

33

parasites may infect other animals, and the converse, through Anopheles ; and it will be noted that
monkeys and bats, in which parasites like the human ones have been found, are closely allied to
man. But while no strong argument can be adduced against this view, not much can be said for
it. In fact the only thing which we can find in its favour is the popular notion that malarial fever
can be acquired in uninhabited localities —a notion which we will presently discuss.

24. Is the Life-History of the Haemamcebidae fully known ? — According to the
known facts, malarial fever is communicated from sick to healthy persons by the bite of Jnopheles.
But a very important question remains. Is this the only way in which the disease can be
propagated ; or do the parasites possess some other cycle of existence, and, perhaps, some other
mode of entry into man ?

Nature is so full of potentialities that we can scarcely ever venture to say absolutely, at
least with regard to any of the lowest forms of life, that we know all their life-history ; but when
one life-cycle is known, we are not justified in believing that there may or must be another, unless
there are grounds for this belief. The lower forms of life, like the higher ones, cannot have an
unlimited number of life-cycles. The life-cycle of the Haemamcebidae as already know 1 is
complex enough — are we to suppose that they possess others r If they can live freely in air and
water ; if they can enter man by the respiratory or digestive tracts ; even if they can pass, not
only from the gnat to man, but also indefinitely from gnat to gnat, they must possess different
phases adapted to these modes of existence and transference, and their whole life-history must be
complex indeed. They must possess not only the known phase which adapts them for life in the
gnat, but other phases which adapt them for life in the soil or water — which enable them to rise
in the air and pierce the epithelium of our respiratory passages, and so on. When we consider
the amount of variation in structure and function which this would entail, we can scarcely be
blamed for refusing to believe in other life-cycles without good evidence.

Is there any evidence which will lead us to suppose that there is or may be another
cycle First, is there any evidence to be drawn from our knowledge of the disease, malarial
fever ? Secondly, is there any evidence to be drawn from our knowledge regarding the parasites
themselves ?

It is often stated that malarial fever exists where there are no gnats ; and that persons
become infected without being bitten by gnats. Were cases of this kind to be substantiated,
they would certainly prove the existence of other modes of infection, either by other suctorial
insects, or by some quite different route. But what value can we attach to popular statements
of this kind ? A perusal of paragraph 16 will suggest how easy it may be for Anopheles to
be overlooked — especially by persons who do not make an express search for them. Moreover,
when we remember that a large number of cases of fever occurring anywhere are relapses, and that
Anopheles may be present only at certain seasons, we must hesitate still more in accepting such
statements ; while the known fact that persons can be bitten without observing it discredits
the other notion. We do not say that all sucli statements are absolutely untrue ; but we are
scarcely justified in accepting them until cases have been established by competent observers.

E

34

REPORT OF THE MALARIA EXPEDITION.

On the other hand, it is impossible to consider the^ matter given in paragraph 2i without
feeh'ng that the gnat-theory suffices to explain almost all the better-established laws regarding
malaria — its connection with the soil, with stagnant water, with rainfall, with rural areas, and
so on. In short, there seems to be no longer any necemty for believing that the parasites live
at all in the air or soil of infected localities. The facts on which we formerly founded our
belief that they did so are now otherwise explained by the origin of Anopheles from surface-
puddles. The facts were sound enougli ; our interpretation of them was wrong. Malarial
fever is connected with the soil, with stagnant water, and so on, as we supposed it is ; but
it is not, as ive thought, the germ itself which springs frotn the soil — but the carrier of the germ.

It is impossible to avoid seeing how completely this fact in the bionomics of Anopheles
subverts the arguments in favour of the view that the pathogenetic organisms themselves have a
telluric or paludal origin.

The idea that the parasites can. originate in the soil, and thence pass into gnats, and
from gnats to man, is opposed to all parasitological, analogy. On the other hand, that they
can pass alternately between men and gnats is merely an instance of a very common law
among parasites.

The fact that malarial fever is communicable from the sick to the healthy has certainly
been a surprising one. We thought that it is not communicable because we observed that
communication does not occur outside endemic areas ; while within endemic areas we attributed
to an endemic poison infections which were really due to communication from the sick. By
endemic (malarious) areas, we now understand simply areas which are infected by the com-
municating agent [Anopheles).

Of course the parasite itself, as well as both the hosts, must be present in an endemic
area. Once present, however, there is no reason why it should not remain indefinitely so long
as both the hosts remain.

So far, then, all the known facts about the prevalence of the disease seem to be easily
explicable by the bionomics of the parasites and of Anopheles ; but we now come to the
consideration of the one popular theory whicli is not so readily explained — we mean the notion
that malarial fever may be acquired in uninhabited places.

As a rule man lives in the society of man. Hence the vast majority of infections must
take place in inhabited places — in places where previous cases of malarial fever have existed
perhaps from time immemorial. Even during the most detached moments men are seldom
quite solitary. Pioneers, explorers, missionaries, travellers, sportsmen, are usually accompanied by
trains of servants and carriers ; in order to reach uninhabited places they have to pass through
native towns and villages ; have to live long perhaps in native houses, and in settled camps
surrounded by their followers. Ships on which malarial fever breaks out have not as a rule
touched at uninhabited spots on the malarious coast, but at towns and ports where trade is carried
on- and may have been visited by infected coolies, or even by infected gnats, from the shore.
In all such instances, cases' of fresh infection may be simply explained by communication from
previously infected men— at least the possibility of this can seldorn be excluded, ^Even In the

REPORT OF THE MALARIA EJiPEDITION.

35

very rare case of complete solitaries, attacks of fever may perhaps often be attributed to relapses
due to a long previous infection acquired in the haunts of men.

Travellers and sportsmen sometimes attribute their fever to having passed througli a
particular uninhabited but " deadly " spot. Such cases are generally questionable. On enquiry
it is often found that the fever has commenced the very day, or the day after, the traveller has
arrived at the place he refers to ; so that the necessary phenomenon of an incubation period is
vi^anting ! A case is on record where a family of healthy natives were found living in one of the
*' deadliest spots " in India [25] ; and we were informed that some persons who escaped from the
Benin massacre, and lived several days in the reputedly deadly jungles, escaped without fever.
It is certainly often possible to explain outbreaks of fever, attributed to such localities, by previous
infection acquired by the suffering party in rest-houses and native villages en route.

If a healthy person could be carried to an~uninhabited but reputedly " malarious " spot in
a balloon, and should then acquire the disease, we should be forced to admit the possibility of
infection in such places. Failing this, it is at least open to doubt whether autochthonous malaria
does in fact exist in uninhabited localities at all.

Even assuming it does so, however, the fact would be explicable witliout the assistance of
another life-cycle of the parasites, on the ground that Anopheles may possibly convey the infection
from wild animals {paragraph 231. For instance, both monkeys and bats are often found in
large numbers in forests reputed to be malarious.

Failing even this, if it can be shown that autochthonous malaria does exist in uninhabited
places, the fact would be more readily explained on the hypothesis that the Hasmamcebida; can
pass from gnat to gnat, than on any other. And this leads to the second question given above.
Is there any evidence to be drawn from our knowledge regarding the parasites themselves in
favour of the view that they possess another life-cycle ?

The Indian observations showed that in many of tlie zygotes of H. relicta found in
C. fatigansy certain large, black, sausage-shaped bodies occurred. These were provisionally called
by one of us " black spores." They occurred not only in the zygotes, but in other parts of the
gnat ; facts which he at first explained on the assumption that they are produced within tlie
zygotes, are liberated on the rupture of these, and are then distributed by the insect's circulation
throughout its tissues in a manner similar to the way in which the blasts are distributed. Later,
however, he observed in gnats which were not infected with Hasmamoebidas at all, bodies which
were very similar to these black spores, but which showed evidences of fission in the manner of
the fission fungi, and indeed of growth entirely independent of the Haimamoebidae. Consequently
he at once modified his statements about these bodies [21], and suggested tliat, though he
could not say for certain what they arc, they may be some parasitic organisms in gnats which
have the power also of invading the z)'gotes of the H:emamu;bida;. He at first tliought that tliey
might be meant for infecting the larva; of gnats, and indeed made some negative experiments in
this connection, but later abandoned all hypothesis on the subject pending further rcsearclics.
Since then the " black spores " have been found by other observers, who also have failed in
elucidating their nature. In Freetown we noted bodies very like tliem in a few Anopheles ; but

36

REPORT OF THE MALARIA EXPEDITION.

tlicsc bodies were never seen within tlie zygotes, while tliey often occurred, mixed with wliat
looked like segments of a fungus, within the slieath of certain muscle-fibres {I'.g., of the stomach),
and indeed appeared to have no relation at all with the Hsmamoebidae.

If these bodies are indeed forms of the parasites, they will certainly suggest another life-
c\ cle. In this case they will probably infect larva-, for the purpose of continuing the species from
gnat to gnat. The probability of one of them ever reaching man's digestive or respiratory tracts
must be so remote that we can scarcely imagine that they are provided for this purpose. In the
meantime it remains to be proved that they have any connection with the parasites at all.

It should also be noted that many full-grown zygotes do not contain blasts,— a fact which
suggests that they may be set apart for some other purpose. At the same time the)' ma)' merely
be zygotes which for some reason have not been able to ripen as early as the rest.

The method of diffusion of the disease by inoculation through the proboscis of gnats
is so perfect a one that, now we are acquainted with it, it seems difficult to imagine the
existence of any other— such, for instance, as the clumsy methods which in our ignorance we
formerly imputed to nature. In the transference of the parasites from man to man by gnats,
there is an economy which would not have existed had nature sown the organisms broadcast
through the soil or air, on the chance of one of them occasionally infecting a human being.

To sum up, then — there appears at present to be no strong evidence, based on our
knowledge either of the disease or of the parasites, in favour of the view that the latter possess
any other life-cycle besides the one wliich is already known. On the other hand, the fact
that malarial fever is communicated from sick to liealthy persons by Anopheles seems sufficient
to explain all tlie well-establislied laws regarding the prevalence and diffusion of the disease.

( 37 )

VI. PREVENTION.

25. Measures Indicated. — It is a well-known fact that malaria has been often eradicated
from certain localities by cultivation and drainage of the soil. Hence we are justified in saying
that the possibility of prevention has been demonstrated in some cases by experience. But
cultivation and drainage are generally large and costly measures, and are often impossible. We
propose now to examine whether the new observations regarding the propagation of the disease
can suggest any cheaper, more precise, or more effective means of prevention.

Since the disease is certainly conveyed by Anopheles^ it is obvious — whether this be the
only mode of propagation or not — that measures taken against these insects in any locality
must assuredly be at least beneficial, even if they do not result in the entire extirpatioi. of
the malady in that place.

King long ago pointed out [i] that if malarial fever be produced by gnats, prevention
of tlic disease will consist in precautions against their bites by mosquito-nettings, window screens,
and inunctions of the skin ; and in measures for the exclusion or destruction of the insects,
such as screens of trees, smoke, fires and lights (in which he supposed they destroy themselves),
and the draining of swamps and pools. Similar ideas have occurred independently to other
observers who have considered the gnat-theory. Nuttall gives [12] a summary of measures
against gnats recommended by various writers — such as draining or dumping the pools, or
flushing them ; or agitating the water by wheels turned by wind-mills ; or the introduction of
small fish ; or by the introduction of gnat-eating birds and dragon flies ; or by the use of
fires, " lamp-traps," and so on, of inunctions to the skin, and of various " culicicidcs," such as
kerosene oil ; or by the plantatioji of water-absorbing trees. Celli and Casagrandi have recently
reconsidered the subject, and have recorded a number of valuable experiments with various
culicicidcs [26].

It will be observed that these measures can be resolved into two classes, namel\- :
(i.) Precautions against the bites of gnats.
(2.) Measures for reducing their numbers.

Of course, if malarial fever be communicated only b)- the bite of gnats, as tlicre is now
every reason to suppose [paragraph 24], these measures will include the entire propli)-laxis against

the disease. If there be also some other method of propagation, other methods of prevention the

nature of which we cannot now indicate —will also be called for.

Note also that we refer only to the prevention of infection, not to the prevention of the
recurrences of fever, which often occur in a patient years after the primary infection, and wiiich
are not connected with the original infective causes at all.

38

REPORT OF THE MALARIA EXPEDITION.

26. Precautions against the Bites of Gnats.— We shall content ourselves with
recording a few practical remarks in this connection.

(i.) Numerous substances have been vaunted as being efficient cuiicifugt's," sucii as oil
of lavender, eucalyptus, kerosene oil, etc. [12]. It is scarcely advisable to trust to any of them
until their value has been demonstrated by experiment. Even if an effective culicifuge exists,
it is hardly to be expected that many persons in malarious localities will use it constantl)^

(2.) Lights in a bedroom tend to prevent gnats from biting — not by attracting them, as
many suppose ; but more probably by alarming them. They seem to prefer darkness for feeding.
Many species of gnats bite voraciously during the daytime, even in verandahs and under trees.
These are generally gnats of the C. t^niatus type.

(3.) In India, natives certainly seem more prone to infection than Europeans. This
may be partly attributed to their wearing less clothing and not generally sleeping in mosquito-
nets. It should be observed, however, that natives of India (and, we believe, negroes) generally
sleep with a sheet drawn over their heads, for the express purpose of keeping off gnats ; and the
method is undoubtedly partially effective.

(4.) Some writers imagine that the darkness of the skin of the coloured races is a preventive
against gnats. As a matter of fact, it will be generally observed that gnats settle on dark surfaces,
and are probably attracted by dark skins, instinct telling them that they are likelv to find their
food there.

(5.) In India it is universally recognised that fans and punkahs keep away gnats to a large
extent. Thus many persons dispense with nets and sleep only under punkahs — a questionable
practice in the presence of Jnophe/es, hcc^us(:, unless the punkah swings rapidly just over the
body, gnats are not much deterred by it.

(6.) Mosquito-nets must be entirely free from holes, because gnats find tlieir way tlirougii
the smallest aperture. They should also have a doubling or valance just above tiie surface of the
bed, in order to protect the hands, feet, and knees of the sleeper when thrust against the net during
sleep. If tlie weatlier is hot the net should not be dispensed with, but a punkah may be employed
over it. The top of the net should be made of gauze. Tent-shaped nets are hot and close
because they fall in folds. A rectangular net, tightly stretched inside a wooden framework, and
carefully tucked under the mattress, is much better. The net should never be allowed to fall to
the floor. Unless care is taken while getting into bed, gnats frequently enter with the occupant.
Mosquito-nets are often used in so stupid a manner that, instead of excluding gnats, they include
them — -gnats which have previously entered being allowed to remain within the net for days.

(7.) Screens to windows are little employed. They would probably be very effective
indeed. They should be made of fine wire with a fairly large mesii, and should be fixed
immovably if possible, because gnats find their way in and out of windows at all times of the day.
They are often employed in America.

(8.) Some persons have such a dislike to being bitten that they are constantly on the watch
for " mosquitoes," and drive them away or kill them whenever possible. Such certainly escape
much more than those who are indifferent to the insects, or those who think they are immune
against tliem.

REPORT OF THE MALARIA EXPEDITION.

39

While it is never possible entirely to avoid being bitten, careful persons can certainly avoid
being bitten to a very large extent by the use of some of the measures indicated above ; and
evidently the less one is bitten the smaller are the chances of infection. Indeed it is probable that
the general neglect of these precautions by a community largely enhances its sick-rate. Thus in
India the natives seldom employ either the punkahs or the mosquito-nets w^hich are so generally
used by the well-to-do whites ; and are certainly much more subject to fever. The poorer
Europeans, also, frequently neglect these necessities ; and also appear to suffer ■ more than the
richer people. We were much struck by the fact that in Sierra Leone both nets and punkahs
were seldom employed— or if nets were used, they were not used effectively ; and we have heard
that they are similarly neglected in many other places on the West Coast. It is not at all
unlikely that this fact will partly account for the fever-rate on the West Coast being so largely in
excess of what it is in India.

That this is not an exaggeration will be more readily perceived by those who possess actual
experience of life in different tropical localities. In some, where nets and punkahs are not
generally used, our lives at the mercy of these insects — it is impossible to sleep, eat, read, or even
in some cases to stand still, without being bitten by them. In others, such for instance as the
large Indian cities and cantonments, where punkahs are kept going all day and nets are jealously
used during sleep, one often lives for several days without suffering a single bite. The risk of
being bitten — and consequently, in malarious' localities, of infection — must therefore be greatly
diminished by these precautions. Assuming that the risk is diminished to one-fourth — and this is
scarcely too much — we may calculate that the fever-rate will be correspondingly reduced by
three-quarters. Prophylactic measures which promise anything like so much are certainly not to
be despised.

Nets and punkahs, then, should always be employed in malarious countries by persons who
can afford them.

Screens of wire-gauze to the windows seem to be especially indicated in public buildings
such as barracks, hospitals, jails, and asylums. In such buildings there are usually large wards in
which a number of persons sleep together. Here — as for instance in the Wilberforce barracks
[^paragraphs 7, 5] — the Anopheles, if they are present, simply carry the infection uncontrolled from
one to the other of the inmates, until finally a large number become infected. Screens would
lirnit both the ingress of the insects, and also their egress for the purpose of laying their eggs.
Thus few insects would gain admission, while those that do would probably soon perish
[paragraph

Lastly, medical men must always remember that patients with gametocytes in their blood
are infective where Anopheles exist, and must be jealously protected from bites in the interests of
other occupants of the same or neighbouring houses.

It will be observed, however, that precautions against the bites of gnats, while feasible to
intelligent and well-to-do persons, are scarcely likely to be employed by the mass of the population,
at least in malarious areas outside Europe and America. Other measures are required for
the prevention of gnat-fever on a large scale,

40

REPORT OF THE MALARIA EXPEDITION.

27. Operations for Reducing the Numbers of Anopheles.— Such operations will be
divided into : —

(i.) Destruction of adults or larva?.

(2.) Measures to prevent the insects breeding.

Where the larvs cannot be found — as at Wilberforce- destruction of the adults can be
resorted to. The gorged females, that is, the insects which are particularlv liable to be dangerous,
can often be killed while seated asleep in the daytime on the walls of a house. The same thing
may be done on^shlps ; and it is quite possible that many infections may be prevented in this
manner. Native servants become very expert at the work. But, of course, such a measure
will not be possible on a large scale.

The most vulnerable point in the history of gnats is when they are larvae ; they can then
be destroyed wliolesale. In the case of larvae in vessels, it suffices simply to pour out the water
on the ground ; but it is more difficult to deal with larva? in pools, drains, cisterns, wells, streams,
drinking fountains, and rice-fields, etc. Even here, however, very simple measures may often
suffice.

Thus small puddles can be brushed out with a broom, the larva? dying on desiccation if
the operation be done in dry weather. We judged that in Freetown 80 °jo of the puddles could
be treated in this manner with little labour.

Other pools can often be evacuated^ or filled up with earth hy means of a few strokes of
the spade. The former, however, may be impossible in perfectly level country.

Where these simple measures are impracticable recourse may be had to " culicicides." The
most popular of these is kerosene oil (paraffin). We found that this can be most easily applied by
means of a rag fixed on a stick. In this manner a number of puddles can be " painted " in a few
minutes at the cost of but little oil ; but enough oil must be used to make a fairly permanent film.
Aaron states that for five dollars sufficient oil can be purchased to make five applications to
100 acres of water [12]. Strachan recommends o/ive oil mixed with a very small proportion of
turpentine, especially for cisterns of drinking water [27]. Nuttall quotes writers as saying that
copperas, and even rusty iron, are culicicides ; certainly larvae are not commonly found in iron
vessels, except when water runs into them as from a tap. Numerous other culicicides are
suggested by the work of Celli and Casagrandi [26].

It is obvious that by these means we can destroy a large number of larvae at any time ;
and it is even possible that by repeatedly dealing with every pool in a given locality we may
ultimately be able to exterminate, or almost exterminate, the insects in that locality. But there is
one serious difficulty. Such operations carried out on a large scale will require constant care,
involving a great deal of trouble and some expense ; while untrustworthy agents will be very
likely to neglect their work. This will especially be the case if the Anopheles pools are very
numerous. It will therefore be generally preferable to deal witli the insects by preventing them
breeding altogether.

Two ways of doing this suggest themselves —

REPORT OF THE MALARIA EXPEDITION.

41

(i.) The whole of the area of operations must be carefully dealt with by draining away or
filling up every collection of water which is found to harbour Anopheles larvae at
any time.

(2.) Some cheap culicicide which will have the effect of rendering the pools permanently
uninhabitable for;the larvae must be employed.

The first will be an engineering work, the details of which need not be considered by us.
Its cost will obviously depend on the number of pools existing in the locality of operations, and on
the natural difficulties in the way of draining them or filling them with earth.

The second measure will depend on the discovery of tlie substance which will have the
effect required. It must be some cheap solid substance which kills larvae without injuring higher
animals, and which, when sprinkled on depressions in the ground, will render the pools which form
there uninhabitable for the larvae for a long time — say for months or longer. Such a substance
has yet to be found by proper experiments ; but we may suggest tar and Uyne as being possibly
suitable.

When placed in water, tar constantly gives off a film like that produced by kerosene oil,
but more permanent. Judging from Dr. Fielding-Ould's experiments [^Addendum II.], it would
seem to destroy larvae in a more effective manner than oil does ; but it remains to be seen how
long its effects will last.

Lime is suggested by a paper by Grellet [28], of which we have seen only a review. Dr.
Grellet gives instances to show that this substance is inimical to malaria ; and cites particularly
tlie example of Chatillon-sur-Loing, where malaria is said to have disappeared as the result of an
extensive application of lime to the soil for agricultural purposes. As it could scarcely have acted
otherwise than by rendering surface pools uninhabitable for Anopheles larvae, we may surmise that
lime may be a substance such as we require.

The fact that Anopheles do not exist in many localities where suitable pools must be
present, suggests that the soil there contains constituents which are inimical to the larvae ; and it
is at least probable that something like the required culicicide actually exists. If it be found, we
may possess a very practicable mode of eradicating the insects from areas which we elect for
operations.

In conclusion, there can be little doubt that we may often be able largely to reduce the
number of Anopheles in some localities by these measures. If we may assume — as it seems we
may — that the malariousness of a locality . depends ceteris paribus on the number of Anopheles
present in it, this would mean that these measures may often enable us largely to improve the
health of certain places.

28. Under what Conditions do Operations against Anopheles promise to be
most Successful? — It will, however, be at once apparent that tiie practicability of employing
these measures in any given locality must depend on two factors, namely, (i) tlie number of
Atiopheles pools present, and (2) the feasibility of attacking the pools.

Judging from the careful study of the question which we made in Freetown, we

F

42

REPORT OF THE MALARIA EXPEDITION.

unanimously came to the conclusion that these operations, if scrupulously prosecuted, promised to
be successful in that town. The pools — at least during the time when we were there, the
height of the rainy season — were not very numerous ; and could easily be attacked, at but little
cost, by any of the measures indicated above. That is, we judged that either if the larvae were
persistently destroyed, or if the pools were carefully obliterated, the insects might be very largely
reduced, if not almost exterminated, in the area studied by us [paragraph 13, Map II.]. It is of
course impossible to speak with absolute certainty on the point until the experiment has actually
been tried ; but from all indications we thought this conclusion was a reasonable one.

But even if the operations ultimately prove to be successful in Freetown, it does not follow
that they will be equally successful elsewhere. The conditions obtaining in Freetown do not
obtain everywhere ; and we have already pointed out that, owing to the hilly nature of Freetown,
the pools there are both limited in number and are easy to drain [paragraph 13]. On the other
hand, the large rainfall in Freetown (163 inches) is favourable to the formation and permanence
of puddles in that place.

Judging from our observations, the number of Anophch's puddles in any given locality at
any one time is likely to depend upon a number of factors, namely, (i) amount and continuity of
rainfall, (2) humidity of the atmosphere, (3) height of the subsoil water, (4) flatness of the ground,
(5) porosity of the soil, (6) presence of small fish in surface puddles, (7) use of wells and of pools
for agriculture, (8) temperature ; and also probably on (9) the chemical nature of the soil, and (10)
presence of some vegetable food necessary to the larvs or even to the adults. Hence we may
expect much variation in the number of Anopheles pools in various localities.

In some tropical countries, as in parts of Assam for instance, vast level areas are almost
under water during the rains. In such places the larvas may abound everywhere ; unless it
happens — and the point requires study — that small fish are too plentiful for them. Here it
will be impossible to drain or fill up the pools.

Again, in Lagos, Strachan [27] and Fielding-Ould [Addendum II.] report that the
pools are extremely numerous, while the ground is so flat that it will be difficult to drain them.

In Freetown the pools are much less numerous than in Lagos, and we think it possible
to attack them with success.

In Accra, Fielding-Ould did not^ succeed in finding a single Anopheles pool when he
was there.

In Secunderabad, in; India, only one pool was detected in a considerable area examined
by one of us — though others might have been overlooked.

In tiie Bolan Pass; malaria certainly exists, though the country approximates to a desert.
In such places pools must be very isolated.

In Travancore, James reports [29] that the larvae are found in pools used for obtaining
drinking-water, and also in the submerged plots of ground in which rice is grown (paddy-fields).

Possiblv the larvs may breed in wells — which are often very numerous in tropical cities.*

Since this was written, Cornwall has described finding Anoflida in^iinused wells in Madras city [30].

REPORT OF THE MALARIA EXPEDITION.

43

Lastly, in many places where there is much forest or undergrowth, it may be impossible
to indicate the pools at all.

Even in localities where the pools are sufficiently few, it may be difficult to deal with
them. This will be especially the case with wells, pools of drinking-water, small streams,
ricc-fields, irrigation pools, and pools on water-logged ground.

On the other hand, operations may be very much facilitated if we can succeed in finding
a cheap substance, such as was alluded to in the preceding paragraph, wliich will prevent the
insects breeding in the pools. Suppose, for instance, that a ton of such a substance will
suffice to keep a square mile of land free from Anophcla for a wliole rainy season, we may
hope to eradicate malaria from our principal towns at but little cost.

Again, as suggested in paragraph 17, if Anopheles live from one rainy season to another
only by continuing to breed in the few pools which remain during tlie dry season, wc ma\'
then be able to attack them with comparatively little trouble at that season. This is an indication
which requires following up. It is difficult to understand how the insects tide over the dry season
in places in which almost every inch of soil is then subjected to a heat sufficient, one would tiiink,
to destroy even the eggs. Unless the adults "hibernate," we may suppose that the larva; still live
in wells, or gardens, or in pools in the bed of watercourses which have nearly dried up. If this
be the case, operations against the insects may be much facilitated.

On reviewing these observations, we shall see that —

(i.) Operations against Anopheles are least likely to be effectual in level, water-logged
localities, and in places where tlie insects breed in pools which cannot easily be found, or cannot
easily be treated.

(2.) Operations will probably be easier in country which is not quite level, or where
tlie rainfall is not great.

(3.) They promise to be very easy in extremely dry places.

Lastly, it goes without saying that we can scarcely ever expect to deal with Anopheles
in large rural areas. On tlic other hand, we may reasonably liope to reduce them, if not to
exterminate them, in the principal centres of population and civilization - tliat is, in just the places
where prevention of malaria would be most useful — provided always that we make intelligent
and persistent efforts to do so.

29. Recommendations. — The method of dealing with malaria by operating against
Anopheles would seem to have tliis advantage over the old method by drainage of the soil — it
promises to be much cheaper. Whereas by the old method wc were obliged to drain the whole
of an infected area — often at great cost- we sliall now be called upon to drain, or otiierwise deal
with, only those spots which are the source from wliich the insects (and, by li)'potliesis, the disease)
emanate.

The fact that drainage has often actually' banislied malaria now only suggests that drainage
has often actually banished Anopheles, By reducing this long-known method to one of greater
precision, wc may now reasonably hope to obtain tlic same effect with greater ease.

44

kEl'ORT OF THE MALARIA EXPEDITION.

Financial considerations liavc frcqucntl)' prohibited the employment of the old method ;
they can scarcely prohibit the employment of the new one — at least in many localities.

Although the new method has not yet been tested by actual experiment, all the scientific
indications support the view that it will be a valid one.

The existence of the disease is in many localities such a serious source of expense, not to
mention loss of trade, prosperity and life, that the small sums required for the prosecution of the
new metliod cannot justifiably be withheld, even tliough it is still in the experimental stage.

Hence we feel justified in recommending that operations against Anopheles be included
among the sanitary measures of local governments and municipalities.

We also recommend that further investigations regarding the prevention of malarial fever
be prosecuted with the energy which our national obligations demand.

(45)

VII. REMARKS.

30. Miscellaneous Remarks. — The following notes may be of interest.

(l.) Destruction of gnats, generally, — It is a most astonishing fact that thougli gnats constitute
a serious pest in nearly all tropical towns, one seldom hears of any efforts being made to control
their numbers. Even Europeans appear to be generally quite ignorant of their source, and often
allow them to breed in large numbers in tubs and flower-pots just outside their windows; and then
complain of their presence and attribute it to the " locality. " It would be a benefit to the
community if medical men would exert their influence with local municipalities in favour of some
action against these insects — not only Anopheles, but Culex as well. A single intelligent native
agent, whose services could generally be obtained for one or two pounds a month, would be able
to do a great deal of good in many towns, simply by going from liouse to Iiouse and emptj ing the
vessels of stagnant water, or by treating them with culicicides, or by showing the occupants what
to do. Sanitary inspectors migiit also be instructed to attend to the matter. The policy of
indiflFerence adopted at present is ridiculous.

(2.) Houses of Europeans in the Tropics. — We have already referred to the fact that punkahs
and mosquito-nets are not as generally used in Sierra Leone as in India. In the latter country
Englishmen seem to have learnt by long experience how best to live in the tropics. Not only do
they employ these comforts wherever possible, but their houses are as a rule specially adapted for
tropical life — they are generally commodious, well-built, and surrounded by a large open area or
" compound." Undoubtedly this must assist in preserving the occupants from a great deal of
fever. Gnats do not like airy, well-lighted rooms ; while, if there is a large compound, infection
cannot be as easily carried from adjacent houses. Moreover, in India there is generally a separate
European quarter, wliich is as a rule built on tlie most elevated site present. In Freetown none
of these precautions have been adopted. In addition to the neglect of punkahs and mosquito-nets,
the houses are small, crowded together, mixed with tlie houses of the townspeople, and built in
the lowest part of the town. Anopheles easily live in them, can bring in the infection from
numerous neighbouring dwellings, and can feed uncontrolled on the occupants ; while they find
numerous pools suitable for them in tJic ditches by the side of the streets.

On the ridge behind Kortright Hill there is a large plateau over lOOO feet above sea-level,
and capable of holding the houses of all the Europeans in the colony.

Serious attention ouglit to be given to this question of the houses of Europeans in the
tropics. It employes are sent at all to dangerous climates, it is the manifest duty of their employers
— whether these employers be the Government or private persons- to see that they are housed in

46

REPORT OF THE MALARIA EXPEDITION.

a manner most likely to preserve their_ health. If the nation wishes to maintain colonies in
intensely malarious localities, the least it can do is to protect its servants as much as possible from
the disease.

(3,) Surface-drainage of Freetown. — This is undoubtedly bad as a rule. The substitution
of simple masonry gutters for the existing roadside ditches would probably have a considerable
effect on the malaria. In some spots, however, it will be necessary to avert drainage from tlie hills.

(4.) Disposal of night-soil, — As already mentioned, a system of pit-latrincs is in use in
Freetown. Not only does there seem to be little dysentery or enteric fever present in tlic citv, but
the disgusting odours so frequent in Indian towns (where removal systems arc adopted) are
comparatively infrequent. In short, it is open to question wliether this pit-system — which wc
have compared to a septic-tank system — is not preferable, if it can be adopted, to the ordinary
Indian interception method. A pipe water-supply must of course exist at the same time ; and tlie
subsoil water must be low.

(5.) Filariic in Anopheles costalis. — In many of the Anopheles caught in the Wilberforce
Barracks we found Filoria. All the stages described by Manson, up to the final motile stage,
were present. We add photographs of an earlier and a later stage — the former from a specimen
considerably distorted by the preservative (formalin).

-. Fiian., in An„phdci cKtaln. \muv. st.igc. %.—Filc,rui in Amfhchi CjuJi^. OMcr stiit'C

It is impossible to doubt that these parasites, like the Hajmamoebida; in the same insects,
were derived from the soldiers ; but unfortunately we were unable to obtain the blood of the latter
at night for examination. One of us liad previously observed F, nocturna in the tissues oi Anopheles
fed on a patient containing the parasites [5].

(6.) Tumba-Jly and Tsetse-fly. — We found these insects in Freetown. Accounts of them
will probabh be published elsewliere.

REPORT OF THE MALARIA EXPEDITION.

47

(7.) Towards the end of our stay in Freetown, one of us was attacked with fever : H.
pritcox being at once found in his blood. From the first there was no rigor. The fever was
continuous, but disappeared (together with the parasites) on the fifth day, as the result of treatment
with quinine. The drug was continued for six weeks, and no relapse has occurred.

(8.) Distribution of Anopheles costalis. — It is always difficult, without elaborate study of
perfect specimens, to come to sound conclusions respecting the species of gnats. So far, however,
as we could judge from specimens obtained from various parts of the West Coast, Anopheles costalis
appears to have a wide distribution there. See, for instance, Strachan [27] and Fielding-Ould
[Addendum II.]. We may even conjecture — pending more certain information — that it is the
principal agent of the deadly West Coast fever.

(9.) Use of the microscope for clinical purposes. — We beg earnestly to recommend that
Laveran's discovery, which has now been made for twenty years, be used in medical practice in
malarious localities. The microscope is called for, not only for diagnosis and treatment, but in
order to obtain exact information regarding the nature of the various fevers prevalent in warm
countries — fevers which often cannot be differentiated by the symptoms alone. For example, we
do not yet know the nature of black-water fever — a point whicli would probably have been
decided long ago if medical men had more generally adopted microscopical methods in their
practice.

(10.) In conclusion, it should be strongly emphasized that many substances which have
not the power actually of killing Anopheles larvae may yet be capable of rendering depressions in
the ground uninhabitable for them for long periods. Common salt may be effective ; but the
range of substances for experiment in this connection is very large. It is to be hoped that such
experiments will soon be made.

FINIS.

(49)

ADDENDUM I.

Description of Two Species of Anopheles from West Africa.
By Major G. M. Giles, M.B., F.R.C.S., I.M.S.

Owing to the sudden departure of Mr. Austen, late of the Liverpool Malaria Expedition, for the
seat of war, I have been asked to draw up a formal description of the two species of Anopheles brought by
the party from the West Coast of Africa. I should however mention that, having run over the specimens
with Mr. Austen, I am indebted to him for many of the points specified, so' that the description m"ght
almost be said to be a joint production.

We are agreed in considering one of the two species as undoubtedly identical with Anopheles costalis,
Loew, originally described by him from CafFraria, but which now appears to have a wide distribution
over, at any rate, a large proportion of the tropical and subtropical African littoral. The other species does
not appear to have been previously described, and, at Mr. Austen's suggestion, has been named Anopheles
funestus sp. n.

The following are the descriptions of the two species in question : —

Anopheles COStalis, Loew. — Wings with the costa interrupted by patches of darker and
lighter colouration, but not generally dark ; the costa has the basal third dark with two minute interrup-
tions followed by three other dark spots, the first of which is the largest, separated by smaller yellowish
interruptions ; portions of the other veins are black-scaled, but the lighter tinted scales preponderate.
Abdomen not distinctly banded, but with the hind border of the segments rather darker, especially in the
male. Tarsi with minute rings, mainly apical, but involving also the base of the next joint.

Description from Loew, Berlin Ent. Zeits, iS66, p. 55.

" ? Pale tinted, with the palpi black with white rings ; wings with uniformly black costal spots.
Length of the body, 2 lines ; of the wings, z'/,^ — z'/g lines.

Clay coloured. The two first joints of the antennas yellow ; remaining joints brownish. Palpi
black, with a white ring on each of their joints. Thorax with a bright brownish longitudinal stripe on
either side, and a distinct brownish line in the middle. Pleurae striped and speckled with pale brown.
The hairs on the thorax, scutellem, and abdomen entirely light yellowish. Legs yellowish brown ; the
femora yellowish at the base ; all the outermost points of the knees and tibiae of a yellowish colouration.
Wings limpid, with pale yellowish, almost white-haired veins, with here and there patches of black hairs,
so as to produce a characteristic marking of the wing ; of these spots the most striking are four placed on
the anterior border of the wing and not extending beyond the first longitudinal vein, and forming
elongated black spots which alternate with clearer portions of the wing-border ; the spots on the remaining
part of the wing are not so distinct, because, owing to the veins being placed further apart, they nowhere
approach each other sufficiently close to admit of their black portions combining to form a noticeable
spot. Habitat — CafFraria, South Africa."

G

50

REPORT OF THE MALARIA EXPEDITION.

In the examples collected on the West Coast, with the exception of the wings, the insect is a
dark brownish grey rather than clay coloured. The palpi of the 9 have the apex broadly white, and
there are, in addition, two narrow white bands on the articulations : further, their scaly covering is rougher
than in An. funestus. The legs are dark brown, somewhat speckled with yellow, especially beneath, but
show nothing of the nature of a band, except on the tarsi. In the fore legs, these have the first three
joints with apical bands, which involve somewhat the contiguous bases of the next joints : in the middle
legs the first three ; and in the hind, the first four joints have purely apical, narrow yellowish bands. The
wings are lighter than in An. funestus., but have a larger proportion of dark scales than in An. rossii, mihi,
or, to judge from his figures, than Ficalbi's pseudopictus and supeipictus. The i has the terminal joint of
the palpi with a dense tuft of hairs, which are brownish yellow internally and blackish externally : the only
other ornament being a very minute ring on the articulation between the second and third joints.

Mr. Austen further makes the following note : — Although this species much resembles An. pktus,
Loew (described from two females from the coast of Asia Minor, opposite the island of Rhodes) in having
the front femora thickened towards the base, I think it is undoubtedly distinct. In the first place, it is
much smaller (only i\ instead of 3 German lines). Then the two last joints of the palpi have an
adornment of yellowish white scales instead of being brown ; and the wings have four dark blotches on
the costal margin in place of three, and all are separate, whereas in Loew's species the first and second
patches are joined together on the costa itself Lastly, the legs difi^er, the tarsi being banded in costalis.

This species forms one of a group of closely allied species, including An. pktus, Loew, An. supeipictus,
Grassi, An. rossii, mihi, An. varius. Walker, and some others, which agree in having the wings with the costal
margin adorned with alternate dark and light spots, while the wing as a whole is not dark tinted. When
closely examined, however, the details of the adornment of the wings, as well as that of the palpi and other
appendages, alFord sufficient points of constant difference to assure us that they are specifically distinct.

The other (and new) species is much more darkly tinted, the white interruptions on the costa and
other veins being so much smaller than the dark portions that it is fairer to call their wings black, with
white spots rather than the reverse. In this respect it forms a link between the paler forms and the
densely black-scaled wings of two species, also new, but as yet undescribed, which were brought back from
India b}- Major Ross, and are now in the British Museum.

Anopheles funestus, Sp. n. — Wings with the costa marked by interrupted darker and
lighter colouration, the dark portions preponderating ; on the actual costa there are five interruptions,
the two basal being connected by dark scales on the auxiliary vein ; there are also white areas over
the transverse veins, the stem of the posterior fork-cell, and the bases of the 5th and 6th longitudinal
veins. Abdomen unbanded, black. Tarsi uniformly black.

9 General colouration black, with but little adornment. Head black, with a crest of scattered
white scales ; eyes with a minute white margin ; proboscis black, a little paler at the apex ; antenna;
black, with scanty whitish verticils ; palpi black, verj- smooth, \\ith the apex and two narrow bands
on the articulations \\hite. Thorax black, clothed with white scales over the greater part of the
dorsum. Legs black, the only relief being a scarcely perceptible paler knee-ring. Wings ornamented as
above described ; the anterior fork-cell long, parallel-sided, with a short stem ; the posterior, much shorter,
wider, and wedge-shaped, with a longer stem ; supernumerary and middle transverse veins of fair
length, in one line, the posterior, shorter and more than twice its length internal to it ; the scales of
the internal fringe with minute white interruptions opposite the junctions of the longitudinal veins
with the margin. Halteres with the knob black and the stem rather lighter. Abdomen black, glabrous,
with very scattered white hairs.

In the i there is no obvious banding of the palpi, but the apex of the last joint is grey,
followed by a narrow black ring, and then by an even narrower pale ring, the rest of the appendage
being of the same funereal tint as the rest of the body. The antenns- are black with dense black
verticils, which, however, show a certain paler lustre in certain lights. The abdomen is black. The
wings, though the)' resemble those of the 9 closely in ornamentation, differ somewhat in venation.

ADDENDA.

51

the anterior fork-cell being twice as long as the posterior, and its stem much the shorter, though both
stems are rather long, while the posterior is very short, and but little wider than the anterior.

Length, excluding the proboscis, 2.6 mm.

Habitat. — Freetown, West Coast of Africa.

Owing to the absence of ornamentation, the description of this species is necessarily brief, but
it will, I trust, suffice to distinguish it from any neighbouring species.

G. M. GILES, M.B., F.R.C.S., Major LM.S.

ADDENDUM II.

Observations at Freetown^ Accra, and Lagos.
By R. Flehlhig-Ould, M.A., M.B.

\. SIERRA LEONE.

In accordance with instructions I joined Major Ross at Sierra Leone in September last, and
during the remainder of his stay there co-operated with him in his researches ; and later, when he
returned to England, I continued the work of the expedition in Freetown.

The habitat and " breeding puddles " of the Anopheles which had been observed infesting the
Wilberforce barracks we had been unable to discover, and I determined to make further and more
rigorous search through the surrounding country than had been possible hitherto. In this I received
the valuable assistance of Captain Smith, R.A.M.C. ; but, notwithstanding the most careful explorations,
we were unable to find any ^»o//^^/^'j^-bearing puddles nearer to the barracks than 1,500 yards. Those
we found were more or less permanent pools in the crevices of rocks below Signal Hill ; and some
others were found in Murray Town. I am inclined to think that these puddles are the puddles that
supply the mosquitoes which infest the barracks. It has been observed that the Anopheles are only to
be found in the barracks intermittently — that is to say, a swarm may be present for two or three days,
and then for a week no mosquitoes are to be seen. This fact, and the impossibility of finding any
puddles nearer than a mile, I venture to explain by the hypothesis that the wind is an important
factor in the matter. The prevailing wind blows over the puddles that I have mentioned in the
direction of the barracks, and by its means, when favourable, the mosquitoes may be able to travel a
long distance — quite contrary to their ordinary habits.

In support of this view it may be mentioned that many facts are on record which seem to
indicate that the poison may be carried to some distance by winds. Again, it has been noticed that
of the two banks of a stream in a malarious district, that towards which the prevailing winds blow is
often the most affected.

During the remainder of my stay in Freetown I was kept supplied b)- consignments ot mosquitoes
from the barracks, and I also obtained some from the houses of natives known to be suffering from
fever. Dissection of these gave substantially the same results obtained by Major Ross. I include with
these notes some drawings, made on the spot, of microscopical preparations, Avhich show various phases
of the malarial parasite in the gnat (Plate IV.)

Out of 29 Anopheles examined by me, six, or 18 per cent., gave definite parasites; while 17
Culex gave in every case negative results.

I made experiments on the puddles at Freetown \vith both tar and kerosene as culicicides.
Both these proved effectual as larva-destroyers, but the former is, in my opinion, likely to prove the

REPORT OF THE MALARIA EXPEDITION.

more successful ultimate]}-. In the same street many puddles bearing larva; were treated — some with
kerosene and some with tar. After 24 hours all were free from larvs. After a further interval the
puddles were again examined ; with the result that all the puddles treated with tar were still free from
larv.-c, while many of those treated with kerosene contained larva;. This result is due to the greater
evanescence of the kerosene film.

II. ACCRA.

RAINFALL AT ACCRA, 1897

On October i8lh I landed at Accra, and after being very kindl}- received by the Governor of the
Gold Coast, who spontaneously offered me all the assistance in his power, I was fortunate enough to meet
Dr. Chalmers, who kindly offered me c]uartcrs, and for whose hospitality and assistance in my work I
cannot too warml}- express my gratitude.

Accra, a straggling town consisting roughly of four parts— native, commercial, official, and
Christiansborg — (r/Vif Map III.) is situated on a perfectly flat plateau on the coast, about 25 feet above
sea level. From the level of the town to the sea-shore stretch broken and crumbling rocks ; and on the
other side, northward of the town, the country is absolutely flat (save for a slight depression here and
there) for 26 miles, until the Aburi Hills are reached.

During my stay at Accra I was unable to find an)- puddles, and consequent]}' Anopheles, notwith-
standing a rigorous search throughout the entire district. To those who know the conditions under

which Ayiopheles ucre found at Sierra Leone this will not be
surprising, for the conditions at Accra are totalh' different ; the
rainfall never exceeds 27 inches per annum, as compared with 170
inches at Sierra Leone. Again, at Sierra Leone the geological
formation is volcanic rock, whereas Accra is built on sand and
gravel ; consequently the small rainfall is very rapidly absorbed b}-
the porous ground. There are no trees, and therefore there is no
shade.

I include here a chart showing the curve of the rainfall
at Accra.

It has been found that the number of fever cases is greatest
during the second quarter of the year, that is to say, just before,
during, and just after the period of greatest rainfall {I'ldc chart).
Another rise in the number of cases occurs in the last quarter ;
when .again it will be noticed that the rainfall increases. At this
time too the " Harmattan " blows, and there is a great fall in the
temperature at nightfall. The increased liability to chill at this
time no doubt, to some extent, explains the increase in the number
of fever cases. I m.ay say that during 1899 the rainfall has been
somewhat less than usual.

Not only was I unable to find an}- specimens of Anopheles
in Accra, but Dr. Chalmers, an enthusiastic entomologist, also
had not seen any during the three months prior to my arrival.
Other kinds of moscjuitoes were present without limit ; and I
seized the opportunity to examine as many of the Culex species as
possible. Fifty-two specimens I dissected, but in none did I find
zygotes. Before deciding that Anopheles is never found at Accra,
we must wait to see if they are present when the rains are at

1

1

1

1

J

1 1

1

<3

\

\

\

/

\

/

\

1

i

J

I

their height, that is to say, in May or June.

'I'licsc being the chief facts x\hich

I obtained as regards the mosquitoes of Accra, one would

53

naturally expect to find that malarial infection was comparatively a rare event there. And this is precisely
what we do find. All my enquiries from local medical men and colonial surgeons led me to believe that
there had been no case of "original infection" for two and a half months before I arrived. During
this time there had of course been " recurrent cases," though these had not been numerous — only thirteen
among Europeans. These, I venture to sa}*, arc important points ; but I do not wish to lay too much
stress on them, for I fully realize that it would be rash to draw too rigid conclusions from observations
carried on over so limited a time ; but it is, in conjunction with facts observed elsewhere, at least
significant of the influence of the mosquito in the propagation of malaria.

It should be noted in this connection that all authorities, in each of the three Colonies that I
had the opportunity of visiting, agreed that 1899 had been an exceptionally healthy year; so that
probably the number of fever cases was below the average.

Thanks to the efforts of the present Governor — Sir Frederick Hodgeson — the official population
is now better housed : spacious and well-ventilated bungalows have been provided, and these have
been removed nearly a mile eastward, so that the native town with its squalor and overcrowding is
no longer the menace that it was {I'ide Map III.). On the other hand, many of the habitations of
the commercial population are badly built and badly ventilated ; some are still in close proximity to
the native huts, and some to that part of the sea-shore which I shall refer to again as practically a
public latrine. To improve the sanitary condition of the native town much has recently been done
in some districts. A fire in 1896 burnt down many of the huts in one part, and afforded an opporfinity
of opening up the maze of squalor that previously existed. Broad streets were laid down, a partial
system of drainage started, a stinking pool in the market place filled up and better houses built — with
the result that disease of all kinds in this district diminished. Several districts remain in all their
primitiveness, and similar treatment could not fail to bring about a marked improvement. But the
Government, though alive to its responsibilities in this matter, arc handicapped by a want of
money for the purpose, and also not a little by restrictions imposed at home by a mistaken and
sentimental regard for what are called " native rights." Alread}- so much has been done with
good results that, in my opinion, advanced with the greatest diffidence, Accra is not the death-trap
its reputation would warrant one to believe. This reputation has been built up partly by the many
cases of sickness imported from the hinterland ; and to get a right conception of the general health
of Accra it is necessary to draw a distinct line between the seat of government and the northern
territories of the colony. I do not mean to say that it will ever become a health resort, nor do I
think it would be wise to extend (as has been by some suggested, including the late Governor, Sir
William Maxwell) the length of the " tour " of service. The climate, quite apart from any specific
disease which may there exist, has a definite reducing and depressing effect on European constitutions.
However healthy a man may be on his arrival on the Gold Coast, sooner or later he becomes ansmic
or dyspeptic, and often his nervous system is so affected that a condition of extreme irritability is
induced ; insomnia often follo\vs, and he becomes totally unfit for work.

It should not be overlooked that the difficulty — often impossibility— of procuring fresh meat and
vegetables is after a time a serious tax on any constitution, however strong. There is a \videspread belief
that alcoholism is rampant on the West Coast ; I may say here that, though I had good opportunities of
judging, I did not find it so in any of the three Colonies I visited.

That part of Accra known as the "native town " {z'lde Map III.) needs further consideration here,
in order to make it clear that what I have already said may not seem exaggerated, and that it is in fact a
standing menace to the health of the community at large.

In this part of the town there are no streets. Winding alleys, unpavcd, and so narrow that two
persons cannot stand abreast, do duty for streets. These alleys have interminable ramifications, and form
so complex a maze that it was found impossible by the surveying authorities to chart them. Numberless
naked children disport themselves in these gutters, and many mangy dogs are seen wandering about under
no control. In addition to these, sheep and goats of a more or less unhealthy appearance roam the
byeways. Filth of all sorts is found lying broadcast in the alleys ; stinking garbage, decaj ing vegetables,

54

REPORT OF THE MALARIA EXPEDITION.

etc. ; and, to crown all, the natives wash themselves openly in the puddles they have made for the purpose.
The children for the most part use these byeways as latrines. Mosquitoes abound, and the odour is often
frightful. The huts are made of mud roofed in with leaves. They are overcrowded to an appalling
extent — 8 or lo persons often occupying a hut 9 or lo feet square. Scattered here and there through this
district are groups of uninhabited, roofless and often ruined huts. These are used by the neighbouring
families as places in which to discharge their refuse, and also as latrines. Every now and then one comes
across a butt or other receptacle filled with stinking water, infested with mosquitoes, and infected with
bacteria. The latter I was only able to examine microscopically. The former ^vere all of the genus Culex
— no Anopheles were found. A complete absence ot any system of drainage completes what to a European
eye is nothing but a noisome and a pestilential district. The danger of such neighbours to the white
population is obvious, and some of the commercial community, as I have said, live very close indeed to
those parts of the town. This danger is, I think, increased by the fact that the prevailing wind sweeps
over and through these native dens before reaching the houses of the white inhabitants. Public latrines
have been indeed provided by the Government on the sea-shore, but I am of opinion that these are
themselves not wholly without danger. Some are flushed by the sea ; but on October 20 two were
entirely dry — and that on a day when the tide was of quite average height. Much of the open sea-shore
is used as a public latrine too ; and it is easy to imagine in such a climate the condition of afi^airs thus
brought about. Any infective material deposited here is liable also to be carried by the prevailing wind
straight to the European quarters. The problem of drainage and general sanitation is no doubt a very
difiicult one to solve in a place which is so flat, and where there is no water supply (the inhabitants are
entirely dependent on a scanty rainfall). But I venture to think much benefit would result from the
running of broad streets through the congested districts of the native population, and the destruction of
uninhabited houses. An attempt is made by the police to keep the streets in a clean and healthy
condition ; but it is impossible to exercise anything but very incomplete supervision over these unlighted
rabbit-warrens. All wandering dogs and other animals not properly looked after should be destroyed, for
that there is a possibility of their carrying diseases I do not think anjone is inclined to deny. I am
disposed to think that the sea latrines should be done away with, and earth-to-earth land latrines
substituted. These latter are used with complete success in some parts of Lagos, though there too there are
some latrines open to the lagoons.

The suburb of Christiansborg sho\vn on the map has no such plague spots as I have described in the
native town of Accra. Here there are broad streets, \vell kept, and for the most part clean ; the houses are
not crowded together, and there is a fairly complete system of drainage. The drains are open, wide, and
made of cement. Between this suburb and Accra there are a few acres devoted to surface pools, ^vhich the
natives enclose to catch the rain for various domestic uses ; and on these pools they are entirely dependent
for their water supply. Some contained mosquitoes (all Culex, no Anopheles), various weeds and alga; ; but
^vere s^veet and clean for the most part.

It may be surprising that so near Accra a suburb with the above characteristics should exist ; but it
is easily explained : Christiansborg Castle was at one time the Governor's residence, and Christiansborg
itself the seat of government. At this time some thousands of pounds must have been spent to produce
the good result I have sketched above. The present Governor is doing everything in his power to improve
sanitation in Accra, and though, as I have said, he is hampered in various ways, slowly but surely an
improved state of things is showing itself.

The authorities and West Coast medical men generally are now fully awake to the fact that all has
not yet been done that may be done to improve sanitation, and in the next few years I anticipate a definite
improvement in this respect, and also a greater activity in scientific medical research. At present any
research is carried on under almost disheartening difficulties. Instruments rust, microscopes and other
lenses become cloudy (even the cover glasses and slides which I took out with me became useless), and
bacteriological research is quite impossible under present conditions.

Now, however, I think I may say a new epoch is about to begin in the scientific study ot
diseases prevalent on the West Coast. The Government of the Gold Coast has sanctioned a preliminary

ADDENDA.

55

expenditure of j^5oo for the formation of a medical research laboratory at Accra, and before I left
I had the pleasure of seeing the building almost ready and fit to receive its scientific equipment. Much,
too, might be done, I venture to suggest, throughout the Colony in this direction. At present no
facilities — not even microscopes — are provided for the assistant or Colonial surgeons on duty in the
hinterland. When one considers that by the microscope we are alone able to diagnose malaria with
certainty, this complete absence of proper instruments is not only appalling, but incomprehensible.
In this connection I may say that there is reason to believe that many cases are wrongly attributed to
the malaria parasite, and earnestly treated with quinine. Were it feasible, though for certain political
reasons it may not be possible, I think better results would accrue if each assistant Colonial surgeon
had a definite district assigned to him with a permanent headquarters, where he might, with a small
outfit of scientific apparatus (at least the microscope, which he is at present without), do much good
work in the interests of tropical medicine. The Colonial surgeons are at present so continuously
travelling (often unavoidably, no doubt), that to expect any scientific work would be ridiculous. But I do
not think that a central research laboratory at Accra — receiving films of blood, pathological specimens, etc.,
for examination — will entirely meet the case, especially in a climate where morbid specimens so rapidly
change their character. There is already a well-appointed and well-managed hospital at Accra, open
for the reception of white and black alike ; and here, too, improvements are being made.

There is no doubt that at Accra the greatest desideratum is a proper water-supply. Up
to the present time, though borings in every direction have repeatedly been made, no water fit for
drinking purposes has as yet been discovered. Rain-water can alone be obtained, and must be stored
in tanks for long periods — during which time it runs great risk of contamination, though every care
be taken. A scheme is on foot to bring water from the Aburi hills, 26 miles away, at the cost of
over 1 00,000. But considering the great expense of this, and the great hindrance to all forms of
business caused by the short term of service imposed by the climate, it is surprising that onl}- during
the last year has the possibility of moving the whole community to Aburi been mooted.

Parasites were not found in any out of 47 Culex examined by me at Accra.

III. LAGOS.-

I proceeded to Lagos, and arrived there on October 27. The Chief Medical Officer of the Colony
(Dr. Henry Strachan) offered me quarters ; and for the great hospitality he showed me during the whole
of my stay I wish here to express my sincere appreciation and gratitude. Lagos is the largest town I
visited. It has roughly 75,000 inhabitants, of which about 150-200 are Europeans. Any estimate of the
population is necessarily only approximate, because the taking of the census is the signal for a general
exodus of the natives for the bush. The town itself is built on an island surrounded by lagoons {virie Map
IV.). The highest point is 19 feet above the level of the water, while, on the other hand, several parts are
actually below sea-level. The island consists geologically of sand deposited on the top of mangrove
swamps ; and borings reveal the existence of alternate strata of sand and decaying vegetable matter. The
swamps (shaded on the map) are seen to almost entirely surround the island. These evil-smelling
quagmires consist largely of mangrove trees and black mud — the latter has a peculiarly offensive odour, due
chiefly, I think, to the evolution of sulphuretted hydrogen gas. Under the microscope I found this mud
to consist chiefly of sand and decaying vegetable matter : many protozoa also were present. The
Europeans live almost entirely in one limited part of the town, their quarters being stretched out along
the edge of the south-western lagoon {vide Map IV.). They are therefore, it will be observed,
surrounded on two sides by swamp and lagoon, and on the other two sides by native habitations. These
latter I need not describe, as they bear a general resemblance to those existing at Accra.

The geological formation of Lagos being such as I have described, it is not surprising that puddles
suitable for the breeding of are plentiful. The island may almost be said to be one immense

puddle ; for the ground everywhere lends itself to the formation of small collections of water and mud on

56

REPORT OF THE MALARIA EXPEDITION.

the occasion of the slightest rainfall. In this respect the contrast presented between Lagos and Accra
cannot fail to be noticed. Anopheles I found to be so widely distributed that it was impossible for me to

make any distinction in favour of one part of the town as compared with another. In every native hut

in all European quarters— in Government House— even in the hospital— I never failed to find some

specimens. My search for parasites was not equally successful ; for, although I dissected 37 specimens, I

was only in one able to satisfy myself of the presence of zygotes.*

During my stay at Lagos there was very little fever ; only two cases were admitted into hospital,

and no out-patients presented themselves for treatment. The blood of both these patients I examined ;

but no parasites were present, though the examination was made on more than one occasion. This did not

however surprise me, for both were mild cases, and had been taking large doses of quinine for six days

before ad mission. Anopheles caught in the wards, and others "fed" on these same two cases, gave also

negative results.

The single specimen in which I found zj-gotes was caught in a native (Hausa) hut ; but I
was unable to trace the cases, and so failed to obtain other specimens. I also, at Lagos, dissected 17
specimens of Culex ; but, as at Accra, these invariably gave negative results. The problem of how
best to deal with the Anopheles and their breeding-places is a peculiarly difficult one at Lagos. The
peculiarities of the soil, and the extreme flatness of the island, render it impossible, in my opinion, for
drainage to be an effectual solution. For similar reasons, and also on account of the universal prevalence
of the mosquitoes — Anopheles — it does not seem to me likely that the application of kerosene or tar to
the puddles will be altogether a successful method. In some few places an attempt has been made to
drain marshy ground into the lagoons, and occasionally this has no doubt done good ; but, taking the
town as whole, this is not feasible, and some other method of extermination must be devised. The
Government, if I may say so, have certainly been acting in the right direction by filling up some of the
more aggressive mangrove swamps with sand ; but this is necessarily a long and tedious business, and
at the best, only a portion of the evil can be treated in this way.

In these swamps, as also at Sierra Leone, I looked for Anopheles, but in neither place did this
particular genus seem to frequent them. Both drainage, as far as it is possible, and the application of
kerosene would no doubt do something to improve matters ; but until some further measures can be
devised, the people of Lagos must rely chiefl)- on the general and less direct means that were recommended
at Sierra Leone, e.g., the intelligent use of mosquito-nets and blinds, etc. — of both of which there is
at present a surprising absence.

The "Rest-House," which is used as temporar)- quarters for Government officials, I found
swarming with Anopheles; and I was able to obtain particulars of several cases of malarial infection
occurring there. Before my arrival, and indeed before the mosquito theory had been brought prominently
forward, several officials dated their fever from nights spent at this " Rest-House " among hosts of what
everyone recognised as a peculiarly vicious variety of mosquito. I am now referring to several well-
authenticated cases, the details of which Dr. Strachan is, I believe, about to publish. From a con-
sideration of these cases one is led to the conclusion that malaria has a definite incubation period of
from 7 to 21 days.

I include here a chart which shows the rainfall, sub-soil water, and fever curves in Lagos for
twelve months. It will be seen that these curves are as nearly as possible coincident, the maximum
number of fever cases occurring a little later than the point of highest sub-soil water. It is impossible
to suppose that this is a mere casual coincidence, and that the two curves have not a definite relation to
one another. The bearing of these observations on the validitj' of the mosquito theory is obvious,
for we know that the Anopheles are most prevalent when the sub-soil water is highest.

It has often been observed in many parts of the world that the upturnings of earth, and
excavations generally, were accompanied by an increase of malaria : it is certain that the turning up of
soil will aggravate the manifestations in districts where malaria is permanently endemic. This has also

* This can be attributed to the gnats not having become previously infected from patients.

ADDENDA.

57

RAINFALL. SUE

AND FEVER

been observed in West Africa, and especially by railway engineers — who perhaps suffer more from fever
than any other section of the white population. I was anxious to see if this could be explained on the
ground that the upturning of earth caused an increase of Anopheles puddles. When, therefore, the
Governor, Sir William Macgregor, M.D., K.C.M.G., invited me to go by special train up the Lagos
Railway from Abutemetta to Aro, I eagerly seized the opportunity. I found that the railway track was
entirely a made track, and that to provide the soil for embankments, etc., many excavated pits had been
made. In some places, for a mile or more these pits remained gaping at intervals of about twenty yards.
In all that I examined there were puddles of varying depth and size, and without exception these puddles
contained Anopheles larvae. This is, to my mind, a point of great interest and importance, and ma}-
entirely explain why in West Africa, at any rate, railway engineers and officials are peculiarly and pre-
eminently exposed to malarial infection.

Throughout the West Coast malaria is ever before
men's eyes as an inevitable evil which all must suffer at some
time or another ; and the result is that any rise of tempera-
ture is immediately diagnosed as malaria, and rigorously
treated with quinine. I saw at least one case in which a
lady suffering from a typical attack of pneumonia (temp.
104° F. ; dyspnoea, complete evidence of consolidation, etc.)
was diagnosed as malaria, was treated with quinine, and was
going to the bad. Fortunately a medical man, comparatively
new to the coast, with a mind open and not befogged by
coast tradition, was called in, and a correct diagnosis made :
the lady recovered with a typical crisis.

This Is a glaring Instance of the tendency on the
coast to diagnose any rise of temperature, be it heat insola-
tion, pleurisy, rheumatism, or even constipation, as malaria.
The absence of microscopes, and the apparent want of belief
in the advantage of microscopical Investigation, Is responsible
to a great extent for this state of affairs ; but traditional
ideas born before the discoveries of Laveran still hold sway,
and cannot wholly be exculpated.

It is noteworthy that black-water fever occurs at all
periods of the year; and, as far as I can judge, its curve
of incidence bears no relation whatever to any of the three
curves on the chart. Black-water fever occurs chiefly among
two classes of the European community, viz. —
{a) Roman Catholic priests and nuns.
{h) German commercial community.
Investigation shows that the connecting link between these
two classes, and the fact that distinguishes them from other
classes, is that they are the most overworked, the worst fed,
and, as a general rule, obtain the least leave to Europe. Some never leave Lagos.

I was Informed that black-water fever is becoming more frequent in West Africa, but that its
virulence Is distinctly diminishing. As In the case of malaria, microscopical examinations of the blood
in black-water fever is the exception rather than the rule, but I never met any medical man in West
Africa who had been able to demonstrate blood-parasites in these cases. From a consideration of these
facts I am Inclined to think that black-water fever will one da>' prove to be a fever sui generis, and wholly
unrelated to the malarial parasite.

In Lagos, again, as in the Gold Coast, I venture to say that the disinterested activity of the English
Schools of Tropical Medicine is bearing good fruit. Before I left I heard that 15 microscopes had been

H

58

REPORT OF THE MALARIA EXPEDITION.

ordered for the use of the surgeons in the Colonial service. A laboratory for research is also being built,
and cannot fail to do good work. In the hinterland, too, facilities for microscopical investigation are being
provided.

There remains the water supply of Lagos to be mentioned. The absence of a proper water supply,
as in Accra, must necessarily bear its share of responsibility for much of the unhealthiness that obtains. In
Lagos, again, the people are dependent on the rainfall alone for their supply of water.

The rainfall in Lagos amounts on an average to 70 inches per annum, and must be stored in tanks
for use during long periods. The risk of contamination is great, and until lately no great effort was made
to keep the tanks in good order. Recently, in consequence of the recommendations of the C.M.O., a
better state of things has been inaugurated, and every effort is now being made to keep the tanks clean and
free from vegetable growth and mosquito larvx. Public latrines are provided by the Government. Some
are open to the lagoons; others, the most sanitary I think, are earth latrines; and it would be well if more
of the latter were provided, and those open to the lagoons closed.

I should have mentioned that there are in places shallow surface wells from which the natives obtain
most of their water : into many of them the sub-soil water drains, and their use can only be viewed with
suspicion.

The hinterland is in many parts healthy, many districts affording high lands and good water, where
white men could live in perfect securitj . It was suggested by the late governor. Sir William Macallum,
that the seat of government should be removed some twelve miles up the railway from Abutemetta. This
should present no insuperable difficulties, and would be an untold benefit to the Government officials, who
form at present a large proportion of the white population of Lagos.

REFERENCES.

r. King. — Mosquitoes and malaria. Popular Science Monthly, Sept., 1883.

2. Laveran. — Traitc des fievres palustres. Paris, 1884.

3. Manson. — On the nature and significance of the crescentic and flagellate bodies in malarial blood.

Brit. Med. Journ., 1894, Vol. II.

4. „ On the life-history of the malaria germ outside the human body. Brit. Med. Journ., 1896,

Vol. I.

5. Ross. — Pigmented cells in mosquitoes. Brit. Med. Journ., 1897, Vol. II. ; and ib.^ 1898, Vol. I.

6. „ Report on the cultivation of Proteosoma Labbc in grey mosquitoes, dated 21st May. Govern-

ment Printing, India, Calcutta. Also Ind. Med. Gaz., 1898.

7. „ Preliminary report on the infection of birds, etc., dated iith Oct., 1898. Government

Printing, India, 1898. Also Ind. Med. Gaz., 1899.

8. Daniels. — Transmission Proteosoma to birds by the mosquito. Proc. Royal Societ}-, Vol. LXIV.

9. MacCallum. — On the flagellate form of the malarial parasite. Lancet, Vol. II., 1897.

10. Grassi, Bignami, Bastianelli. — Numerous papers. Rendiconti della R. Accad. dei Lincei, 1898

and 1899. Also, Annali d'Igiene Sperimentale, 1899.

11. Koch. — Ueber der Entwickelung der Malariaparasiten. Zeitschrift fur Hygiene, etc., 1899.

12. NuTTALL. — Neuere Untersuchungen iiber Malaria, etc. Hygienische Rundschau, 1898, 1899. Also,

On the role of insects... on the spread of diseases. Johns Hopkins Hospital Reports,
Vol. VIII., Baltimore.

13. Ross. — Report to Director-General Indian Medical Service on the extermination of mosquitoes, dated

1 6th February, 1899. See Ind. Med. Gaz., 1899.

14. „ On the possibility of extirpating malaria from certain localities by a new method. Brit. Med.

Journ., July ist, 1899.

15. ,, Life-history of the parasites of malaria. Nature, August 3 rel, 1899.

16. Wilson. — Notes on malaria in connection with meteorological conditions at Sierra Leone, 1899.

H. K. Lewis, London.

17. DuGGAN. — The parasite of malaria in the fevers of Sierra Leone. Medico-Chirurgical Trans.,

Vol. LXXX., 1897.

18. Bancroft. — On the metamorphosis of the young form of Filaria bancrofti^ etc. Journ. Trop. Med.,

Nov., 1899.

19. Grassi and Dionisi. — II ciclo evolutivo degli emosporidi. Rendiconti della R. Accad. dei Lincei,

1898.

20. Mesnil. — Coccidies et paludisme. Revue Gen. des Sciences, 1899.

21. Ross. — Report on the nature of kala-azar, dated 13th January, 1899. Government Printing, India,

Calcutta.

22. Report of the Liverpool School of Tropical Diseases, 1899.

23. Giles. — A description of the Culicida- employed by Major R. Ross. Journ. Trop. Med., 1899.

24. Dionisi. — I parassiti endoglobulari dei pipistrelli. Rendiconti della R. Accad. dei Lincei, 1898.

25. Ross. — Report on a preliminary investigation into malaria in the Sigur Ghat. Ind. Med. Gaz., 1898.

26. Celli and Casagrandi. — Per la distruzione delle zanzarc. .Ann. d'Igiene Spcrimentali, 1899.

27. Strachan. — Notes from Lagos, West Africa. Journ. Trop. Med., 1899.

28. Grellet. — Revue Scientifique, Oct. 21st, 1899, p. 530.

29. James. — The collection of mosquitoes, etc. Ind. Med. Gaz., 1899.

30. Cornwall. — The extermination of malaria. Ind. Med. Gaz., Jan., 1900.

DESCRIPTION OF THE PLATES.

NOTE. — P/afcs I., II., and III. consist of photographs taken mostly from unstained preparations
preserved in formalin. Formalin accentuates the outline of the zygotes ; on the other hand, a small amount of
detail has been lost in the collotype process. Hence the result is that the photographs show the parasites almost
exactly as they are seen in fresh preparations of the tissues of the gnat, except that the granules of melanin
do not come out with sufficient clearness in all the figures. None of the photographs have been in any way
retouched by hand.

PLATE I.

Figure i (x 500). — Very small zygotes of H^emamceba relicta attached to stomach wall of Culex fatigans.

The melanin has become enlarged by the formalin. Coloured.
Figure z (x 500). — Very small zygotes of H. relicta attached to stomach wall of C. fatigans. Unstained.

The melanin is of the natural size.
Figure 3 (x 500). — Very small zygotes of H. vivax attached to stomach wall of Anopheles costalis.

Unstained. Melanin scarcely appreciable in the collotype.
Figure 4 (x 500). — Very small zj-gotes of H. malarije in A. funestus. Unstained.
Figure 5 (x 500). — 'iixn^Xi T.ygo\.&i, oi Hamomenas precox xw A. costalis. Unstained.
Figure 6 { x 500). — Small zygotes of H. malaritr in A. costalis. Unstained.

PLATE II.

Figure 7 (x 500). — Larger zygotes of H. relicta in C. fatigans. One well shown protruding into the

body cavity of the host. Unstained.
Figure 8 (x 500). — Still larger zygotes of H. vivax in A. costalis, showing great delicacy of the outline.

Unstained.

Figure 9 (x 500).— Medium sized zygotes of one of the human species in A. costalis. The focal plane

is taken through one of the blastophores (in the middle of the zygote). The tlasts are already

nearly mature. Unstained.
Figure lo (x 500). — A zygote of H. relicta about two-thirds of the full size, protruding into body cavity,

and containing blasts which are already nearly mature. Unstained.
Figure 1 1 ( x 500). — A full-sized zygote of H. relicta full of mature blasts, many of which are seen to be

packed side by side (near the lower margin). Unstained.
Figure 12 (x about 60). — Stomach of C. fatigans with mature zygotes of H. relicta, as seen by a low power.

Coloured.

PLATE III.

Figure 13 (x 500). — Mature zygote of H. relicta full of blasts ; and also capsule of another (to the left)

containing " black spores." Unstained.
Figure 14 (x about 400). — Blasts and "black spores" of H. relicta in C. fatigans, apparently ejected

together from the capsule of a zygote. Unstained. The "black spores" do not seem to be

mature.

Figure 15 (>« 400). — Blasts of H. relicta lying free in the juices of the thorax of C. fatigans. Unstained. _

Many lie in perspective.
Figure 16 (x 500). — Four blasts of//, relicta in juices of C. fatigans, dried and stained.
Figure 17 (x 500). — Blasts of H. relicta, dried but not stained.

Figure 18 (x about 400). — Blasts of one of the human Hasmamcebidas in the salivary gland of A. costalis.
Unstained. The blasts are closely packed within the salivary cells, and also lie outside the cells,
within the capsule.

PLATE IV.

Drawings, by Dr. Fielding-Ould, of the Haemamcebidac found by him in Anopheles in Sierra Leone.

Figures 1-9. — Zygotes — apparently of H. vivax.
Figure 10. — A zygote discharging blasts.
Figure \ I. — Individual blasts.

PLATE V.

Drawings of Anopheles costalis and Anopheles funestus. Made at the British Museum.

PLATE II.

PLATE III

17.

18.

4.

George Fhahp A Son London AUverpooI