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s

LIVERPGDLSCHCJDL
OP TROPICAL

/AE-PICINE-DD

FIRST
PROGRESS REPORT

OF THE

Campaign

AGAIITST

Mosquitoes

Sierra Leone

j

HAECOT1 A STADIA FOV&jjfP

UVeRPGDL VNIVL^SITV PRESS

HA*V**D UNIVERSITY
not OF MEDICINE AND PUBLIC HEALTH
LIBRARY

8 JUN1948

LIVERPOOL SCHOOL OF TROPICAL MEDICINE
Memoir V. Part I

FIRST PROGRESS REPORT

OF THE

Campaign
Against Mosquitoes

In SIERRA LEONE

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

WALTER MYERS LECTURER
LIVERPOOL SCHOOL OF TROPICAL MEDICINE

Dated Liverpool, xyh October, 1901

AT THE UNIVERSITY PRESS OF LIVERPOOL 1901

- HAWVAWD UNIVERSITY
VHOOL OF MEDICINE AND PUBLIC HEAUW
LIBRARY

8 JUN 1948

No. 25. October, 1901. 1000

REPORT

Dated Liverpool, 15th October, 1901

Preliminary

THIS enterprise was undertaken in the following
circumstances : — Shortly after the development
of the parasites of malaria in mosquitoes had
been determined by my researches of 1895-98, I
suggested that the proper way to extirpate malaria in
towns and cantonments would be to drain the breeding
places of the insects which carry the disease.* All
efforts to induce the authorities to adopt this idea
remained, however, almost entirely unavailing during
two years ; f and at last I resolved upon starting the work
by thefhelp of private enterprise. On the 1 st May, 1 90 1 ,
I received from a gentleman with whom I have the
honour to be acquainted the sum of one thousand
pounds with which to commence the work ; and this
amount he has since doubled. The project was adopted
with energy by the Liverpool School of Tropical

* Letter to Government of India, 16th February, 1899, partly published in
Indian Medical Gazette, July, 1899 ; also Britisk Medical Journal, 1st July, 1899 ;
also Lancet, 1900, vol. ii, page 1400 ; also Journal of the Society of Arts, 30th
November, 1900.

\ The admirable measures instituted against malaria in Lagos by Sir W.
MacGregor and Dr. Strachan are conducted largely on different lines ; and the
operations of Young and Thomson in Hong Kong, and of others elsewhere, have
been very limited in area. I shall presently refer to the work in Havana.

Medicine ; and supplementary gifts and assistance of
all kinds were given by Alfred L. Jones, Esq., J. P.,
John Holt, Esq., F. Swanzy, Esq., Professor Boyce,
Max Muspratt, Esq., Dr. Kohn, and other gentlemen.
Mr. Logan Taylor, M.B., B.S., of the Pathological
Laboratory of Glasgow University, was appointed to
superintend the operations ; and Freetown, Sierra
Leone, was selected to be the site of the experiment,
partly because its malaria had been already surveyed
by the scientific expeditions of the Liverpool School of
Tropical Medicine and the Royal Society, and partly
because the place is so difficult to deal with on account
of the heavy rainfall and the nature of the soil that it
affords a fair, and, indeed, somewhat severe test, of the
feasibility of the measures recommended by me. As
showing the popular interest in the matter, I may
mention that the expedition was entertained by
Mr. Alfred L. Jones at a valedictory banquet,, which
was honoured by the presence of the Lord Mayor of
Liverpool, the Lord Bishop of Liverpool, the Director
General of the Indian Medical Service (Surgeon-General
Harvey, D.S.O., C.B.), the President of the Royal
Institute of Public Health (W. R. Smith, Esq., M.D.,
F.R.S.E.), and other distinguished guests. The Right
Honourable Mr. Joseph Chamberlain, H.M. Secretary
of State for the Colonies, signified his approval and
support of the scheme, and the expedition left England
on the 15th of June.

Commencement of Campaign

We arrived at Freetown* on the 2nd of July, and
were very hospitably entertained by His Excellency the
Governor, Sir Charles King Harman, K.C.M.G. At

* Freetown contains 30,000 inhabitants.

a public lecture, at which His Excellency presided, a
resolution in support of our efforts was unanimously
adopted.

Dr. Logan Taylor commenced work without delay.
In my first suggestions for controlling malaria 1 had
recommended measures against mosquitoes of the genus
Anopheles only ; but mosquitoes of the genus Stegomyia
-have now been conclusively proved to carry yellow
fever ; and mosquitoes of the genus Culex have long
been known to carry Filaria nocturna (elephantiasis).
Malaria and elephantiasis prevail all down the coast ;
and many medical men of repute consider that yellow
fever also has existed there from time to time. In
addition, it is beginning to be thought by some that
mosquitoes may carry other diseases, especially various
tropical fevers distinct from malaria and typhoid ; and,
altogether apart from their pathological agency, most
kinds of mosquitoes undoubtedly cause an immense
amount of annoyance in the tropics, and, next to the
heat, constitute perhaps the principal drawback of life
in warm climates. We determined, therefore, to push
our campaign against all kinds of mosquitoes indis-
criminately.

Dr. Taylor immediately engaged the services of
over twenty men, under intelligent head men. To these
His Excellency the Governor added twelve men, and
gave the necessary carts and implements. This force
was divided into two gangs ; a small gang of six men
(called the Culex gang), to collect from private houses
all the broken bottles and buckets, empty tins, old cala-
bashes, and similar unconsidered vessels in which mos-
quitoes of the genera Stegomyia and Culex breed ; and
a larger gang (called the Anopheles gang), to drain the
pools and puddles in the streets and the backyards of
the houses, in which Anopheles breed.

Progress of Campaign

The Culex gang, under a native headman, did very
rapid work. They piled the rubbish into carts, which
then discharged it into an assigned rubbish shoot. At
the same time they showed the larvae to occupants of
houses and instructed them in the manner of destroying
them by emptying the vessels which contain them, or
by dropping a little oil on the surface of water in which
they live. It was found that on the average this gang
cleared about fifty houses, and removed about ten cart-
loads of empty tins and broken bottles daily. The
effect of this work on the prevalence of Culex and
Stegomyia can be imagined when it is remembered that
about one-third of the tins and bottles contained the
larvae at this season (the rains). Every house had
previously been breeding mosquitoes in its own backyard
or garden. The occupants welcomed the gang where-
ever it went, and some stated that they had not been
able to get rid of their rubbish for years.

The Anopheles gang had a more difficult task.
The breeding-pools of these insects in Freetown, both
in the rains and the dry weather, have been minutely
described by two previous scientific expeditions.* At
this season the water courses contained impetuous
torrents too rapid for larvae to live in ; but the streets,
yards, and gardens possessed numerous pools of rain-
water, well suited for them. These were attacked by
many methods. Some were filled with earth, rubble,
and turf. Others were evacuated by cutting through
the rock which contained them, or by making channels
in the soft earth. Owing to the large rainfall (estimated
at about one hundred and sixty inches annually), to the

* Report of the Liverpool Malaria Expedition to Sierra Leone, University
Press, Liverpool, 1900 ; and Reports of the Malaria Committee of the Royal Society,
Harrison & Sons, St. Martin's Lane, London.

7

peculiar nature of the ground, and to the very defective
surface drains, these puddles were exceptionally numerous
in Freetown ; and, in order to drain many of them as
soon as possible, it was deemed advisable to adopt the
simplest and least expensive methods at first, and to
reserve more permanent works for the future. At the
same time several men were specially employed in
brushing out with brooms, or treating with crude
petroleum or creosote, those puddles which the workmen
had not yet had time to touch. Progress was fairly
rapid in spite of the deluge of rain ; and many of the
worst streets were fairly well drained in a few weeks.*

On the 22nd of July, I left Sierra Leone in order
to visit Lagos and the Gold Coast. A few days later
Lieutenant McKendrick, M.B., of the Indian Medical
Service arrived. The government of India, to whose
well-advised action in 1898 so much is due, had deter-
mined, on the initiative of Surgeon-General Harvey, to
send Lieutenant McKendrick to study our operations in
Freetown. Dr. McKendrick remained there for a month.

I returned to Sierra Leone on the 1 6th August,
and, after witnessing Dr. Taylor's excellent work, left
after five days, in company with Dr. McKendrick for
England, on private affairs. Shortly after my departure
Dr. Daniels, Superintendent of the London School of
Tropical Medicine (conveyed by the Liverpool School),
arrived on the same errand as Lieutenant McKendrick.
He also remained some weeks with Dr. Taylor, and
studied his methods with great care. His report on
the subject will be given at the end of this report.

In letters, dated the 17th and 28th September,
Dr. Taylor says that progress has been satisfactory,

* The proper methods of dealing with mosquitoes are given in detail in my
forthcoming work called Mosquito Brigades, and Hoiv to Organize Them ; George
Phillip & Son, 32, Fleet Street, London ; price three shillings.

although impeded by heavy rain. The Culex gang had
cleared 6,500 houses up to the former date, and, I cal-
culate, must have removed more than a thousant cart-
loads of rubbish. The total number of workmen
employed, including the twelve lent by the Governor,
now number fifty-three. His Excellency has also given
Dr. Taylor the assistance of Dr. Berkeley, of the Col-
onial Medical Service, who had previously done much
useful work in Freetown in this connection. Major
Smith, the able head of the Royal Army Medical Corps
in Sierra Leone, is taking active steps to expel mosqui-
toes from the various military barracks. Drs. Daniels
and Taylor have been able to inspect several places at
a distance from Freetown, with a view to starting work
there also. Two men are specially employed in keep-
ing the centre of the town free from mosquitoes, while
the Culex gang is working elsewhere ; but as this gang
had cleared nine-tenths of the town up to the 28th
September, it will now be able to commence at the
centre again, and perfect its former work.

As the rains are now ceasing, the dry-weather
operations will shortly begin. These will consist chiefly
in attacking the drying water courses, in which Ano-
pheles chiefly breed at that season. Dr. Taylor is already
beginning the work from the 1st October, by filling
hollows in rocks with concrete. These operations will
be detailed in a future progress report. It is possible
that a hundred or more men will have to be employed
shortly.

Results up to the present

It is always very difficult to make an exact estimate
of the number of mosquitoes anywhere, and, therefore,
to gauge their increase or diminution with mathematical

certainty. For the present we must rely on a general
consensus of opinion. Judging from this, the results
are already most encouraging — indeed unexpectedly so.
Lieut. McKendrick informs me that he was not con-
scious of having once been bitten by mosquitoes during
his month's stay in Freetown. After the first week or
so, I myself was never bitten, either at Government
House* or at the house of the Expedition, in the centre
of the town, though I am sure I should have been
bitten several times a day in both, before the commence-
ment of operations. Dr. Taylor writes on the 1 7th
September, ' I think there is no doubt but that the num-
ber of mosquitoes {Anopheles) in the streets we have
dealt with is diminishing ; the people resident in the
streets will tell you that at once ; and the number of
pots and tins that have been removed has made a con-
siderable diminution in the Culex ' — meaning also Steg-
omyia. On the 28 th September, he writes, ' The mos-
quitoes are still on the decline, and in the streets we
have been working in it is exceedingly difficult to find
Anopheles now. Of course in the untouched parts they
are still to be got. As for the Culex (or Stegomyia, to
be correct) they have got a fright. They also are
getting very scarce. The true Culex I seldom see ;
only now and again.' What this means in a tropical
town only those who have resided in such can know.

The valuable testimony of Dr. Daniels to the
same effect is given in his report at the end. All those
who are familiar with his important work on malaria
and other tropical diseases will know that he is one of
the most cautious and trustworthy of observers.

Altogether I think that we have reason to be more
than satisfied with the progress made.

* Capt. Hodgins, A.D.C. to the Governor, had partially cleared Government
House of larvae before our arrival.

IO

Accounts

It might be imagined that all this work has been
very expensive. On the contrary the expense has been
slight. The whole cost of the expedition from its be-
ginning, including cost of fitting out, salary of Dr.
Taylor, wages of from twenty to forty workmen, and
of eight hammock boys, rent and fitting of the house
of the expedition, and other items, had amounted, at the
end of September, that is for three and a half months,
to only £304. This is exclusive of passages, oil,
cement, and of the services of carts, and of twelve men
lent by the governor. The wages of the workmen
may be put roughly at about one pound a month each.
Detailed accounts have been submitted to the School
Committee and to the subscribers.

Other Expeditions

On passing Bathurst, and during my visit to the
Gold Coast, I was able to arrange with Sir George
Denton, K.C.M.G., and Major Nathan, C.M.G., Gov-
ernor of the Gambia and the Gold Coast, to start similar
work in Bathurst, and in the principal towns of the
latter colony. Consequently, Dr. Everett Dutton,
Walter Myers Fellow, was despatched to Bathurst
to make a preliminary survey of the subject there — a
thing which had not yet been done ; and to start some
operations against mosquitoes, with the help of the
governor, and of a sum of money from the Sierra
Leone fund. As regards the Gold Coast, a handsome
sum of money has been specially placed at my disposal
by a philantrophical gentleman to pay the salary of a
delegate ; and I am happy to be able to state that Dr.
Balfour Stewart has accepted the post. Details of these
expeditions will be given in later reports.

II

Anti-Malaria Work Elsewhere

Some of the earliest work against malaria performed
on an anti-mosquito basis was that of Young and
Thomson at Hong Kong, especially at the military
sanatorium, round which the bush was cleared and the
breeding places drained.* Similar work has recently
been done by Dr. Doty near New York, in connection
with an outbreak of malaria in a collection of a hundred
houses in Staten Island.f On a large scale, anti-
mosquito work seems to have been first commenced a
month or two before the operations in Sierra Leone by
Major and Surgeon Gorgas in Havana, immediately
after the demonstration there of the fact that Stegomyia
carries yellow fever.J Havana contains two hundred
and fifty thousand people. In April, Gorgas reports
that he has transferred two-thirds of the town cleaning
gangs to the mosquito brigades. In May, he says,
' most of our attention is now being paid to the
destruction of mosquitoes. The suburbs, and all the
small streams in the suburbs, have been pretty thoroughly
cleared out ; and the pools oiled and drained. The
Mayor has issued an order prohibiting the keeping of
standing water anywhere within the city limits, unless
made mosquitoproof. This is being enforced ; and all
standing water found not protected as required is
emptied and the owner fined. We are employing
seventy-five men in this mosquito work, and have gotten
over the whole city during the last month, and I expect
to do this every month during the summer, at any rate
as long as it seems to have the present happy result.
In this way, during the past month, we have used about

* British Medical Journal, 1901, vol. ii, page 683.

\ Boston Medical and Surgical Journal, 22nd August, 1901 ; and British Medical
Journal, vol. ii, page 644.

X Monthly Reports of Vital Statistics of Havana, Office of Chief Sanitary
Officer of Havana.

12

one thousand four hundred gallons of oil.' The
Americans deserve much credit for the commonsense
and energy with which they have attacked this question ;
so different from the hesitation and apathy generally
shown by the British.

Regarding the prevention of malaria by other
means, we have first the distinguished work of Koch,
based on the general use of quinine,* and more recently
the no less excellent work of Sir William MacGregor,
K.C.M.G., C.B., and of Dr. Strachan at Lagos, based
upon quinine, wire gauze to windows and doors, and
drainage of marshes. f Much work is said to have been
done by the use of wire gauze and quinine in Italy, but
I regret that I cannot accept without reserve all the
statements made on the subject in that country.

Remarks

It may be advisable to correct some popular errors
regarding the operation of clearing mosquitoes. No
one has ever supposed it possible to exterminate
mosquitoes from whole continents, or even from large
rural areas — the operation must be confined principally
to towns and their suburbs. No one imagines that it
will be possible to exterminate every mosquito even
from towns— we aim only at reducing their numbers
as much as possible. No one supposes that it will be
invariably possible to drain or otherwise treat every
breeding place of mosquitoes in a town ; but even
where every place cannot be dealt with, it will always
be possible to deal with a very large number ; and it
often happens that the smallest and most easily drained
or emptied puddles or pots breed the greatest number

* Deutche Medicinische Worchenschrift, 1899, 1900 ; and Journ. of State
Medicine, October, 1901.

-f- British Medical Journal, 1901, vol. ii, pp. 644 and 680

13

of mosquitoes. Mosquitoes may possibly be carried
into towns from a large distance by winds, though I
doubt whether there is much or any reliable evidence
in favour of this view ; but, as a general rule, the vast
majority of mosquitoes existing in a town are bred in
the streets, yards, gardens, and houses of the town ;
and if we get rid of these breeding-places, we may
calculate on at least greatly reducing the insects in the
town. These are the simple principles upon which
our efforts are based.

As regards the effect of such measures on mosquito-
borne disease, we may expect speedy results in the
case of yellow fever, which is not a lingering disease ;
but in the case of malaria and filariasis, which linger
for years after the first infection, good results may not
be so immediately manifest. But science assures us
that we may continue to work in complete confidence
of good results being finally obtained. We know from
the experience of ages that drainage abates malaria.
And, quite apart from sanitary questions, we shall all
admit without argument that the extermination of
mosquitoes in tropical towns will constitute one of the
greatest possible reforms ever made in life in the
tropics.*

{Signed) R. ROSS

* I estimate, for several reasons, that the amount of a mosquito-borne disease
in a locality should vary roughly as the square of the number of mosquitoes capable
of carrying the disease found there. Hence, if the Anopheles are reduced to one-half,
the malaria should (finally) be reduced to a quarter ; if the Anopheles are reduced
to one-tenth, as should generally be practical, the malaria should be reduced to
one-hundredth. But this is an estimate founded merely on a priori considerations ;
and it will always be a matter of great difficulty, especially in native towns, to
pbtain reliable statistics of the variation of the amount of malaria,

APPENDIX

Letter from C. W. Daniels, Esq., M.B. Cantab.

Note. — In reading this letter it is necessary to remember that
Dr. Daniels inspected the Sierra Leone operations little more than
two months after they had been commenced. See also the remarks
under the headings. Progress of the Campaign and Results
above— R. Ross.

ist October, 1901
Dear Ross,

I have carefully examined the various works which
have been undertaken with a view to the serious diminu-
tion in the number of mosquitoes in Freetown, Sierra
Leone. The common mosquitoes found are : — Ano-
pheles costalis, the carrier of malaria, and also of Filaria
nocturna. Stegomyia fas data (Culex taeniatus) or brindled
mosquito, Calcutta, the mosquito supposed to carry
yellow fever.

Tv/o Culices (I think, fatigans, which carries Filaria
nocturna, and another which is known both on the East
Coast and Shire and Uganda Highlands, but does not
attack man) were found, but not commonly.

A. funestus was found near but not in Freetown.

In my opinion, already your efforts have been
crowned with a large degree of success, as there has
been a noteworthy diminution in the number of the
first two genera found in the houses. The number of
breeding grounds has been enormously diminished.

The operations, having been only recently begun,
are, of course, as yet far from complete. A consider-
able part of the town, perhaps half, has not been touched.
Even in the parts longest under treatment, in the yards

i6

adjoining the streets, there are still numerous breeding
grounds ; and in the streets themselves occasional places
have either been overlooked or the works undertaken
have not been effective as yet.

The breeding places dealt with could be only of
importance in the peculiar circumstances of Freetown,
i.e., where the soil is impervious and the rainfall excess-
ive (no in. to 200 in.). Even in Freetown most of
them would be destroyed by a week's dry weather, and
some by less. As, however, the wet season in Sierra
Leone is a prolonged one, for this place these breeding
grounds are of great importance, and in dealing with
them an excellent beginning has been made.

A great part of the work will not be permanent.
The rock cuttings are too narrow, many of them being
blocked after each shower. The earth cuttings are also
very liable to fall in. This results in much extra work
and supervision, as considerable supervision and labour
is required, constantly, to keep the work already done
in order.

I suggest that during the dry season the rock
cuttings should be broadened, so as to be at least three
inches at the bottom, the sides being inclined at about
6o°. When the rush of water is greater a broader
cutting will be requisite.*

The earth cuttings should in all cases have sloping
sides where possible, as this minimises the liability to
formation of pools, and ensures, even with a small
amount of water, a persistent current. There are few
things more suitable for Anopheles breeding grounds
than a drainage system in which the water supply is in-
sufficient to flush the drains.

* Exact uniformity is not essential, but an approximation to it will save a
large amount of labour in clearing the channels ; and as this requires to be done
very frequently, the point is of importance,

17

The plan adopted of placing large stones at the
edge of the channel, blocked behind by smaller ones,
will, I think, suffice if the work is strengthened with
cement ; but brick drains would be preferable in my
opinion, as they are easier to clear.

A large amount of work has been done by filling
up rock pools with small broken stones, and, even where
the traffic is great, this, when strengthened with cement,
will prove to be permanent.

The work is so far incomplete that it is essential
that at least one other complete wet season should be
spent here. Constant European supervision is necessary,
and one man is not sufficient for the purpose. There
should be at least two Europeans engaged in supervising ;
and a larger staff" of workmen (quite twice the present)
would, I think, be required, as so much of the work will
require redoing, and there are other places to deal with.

Towards the foot of Mount Aureole there are in
places numerous springs from which the water is
constantly running. Pits, usually shallow, have been
dug in this district, and in these Anopheles larvae are
constantly found. Some of them will be difficult to
deal with by cuttings alone ; and the more permanent
should, I think, be converted into covered wells with an
overflow underground — say two feet below the surface
— leading into a drain to the nearest stream. None of
these places have, as yet, been dealt with.

There is one similar place in the Grassfields Dis-
trict, and I feel sure that there are others both near the
Wilberforce Barracks and near Kissy. The constant
rains and the general waterlogged condition of the
ground prevent more definite information being obtain-
able till there is some continued fine weather. Such
places are common, and are the important ones in the
hilly districts of Central Africa.

i8

In a few of the wells, which are so numerous in
many districts of Sierra Leone, Anopheles (costalis) larvae
were found in numbers. Though I do not think from
previous experience that these will at any season in the
year be of very great importance, still they are an
additional source. In none of the broad public wells
which contain fish were larvae found, and on placing a
few fish in one of the infested wells the larvae speedily
disappeared, but many of the fish died.

Covered wells in any case are safe ; but to so
repair the numerous broken-down wells and provide
them with covers would be costly and uncertain, as the
covers would not be used in many cases.

I am informed that there would be serious diffi-
culty in closing these private wells, and in substituting
for them a smaller number of public ones, but that
when a good town water supply is obtained much could
be done in this direction. Such a water supply, it is
expected, will be shortly sanctioned.

Equally dangerous are the numerous pits remain-
ing from disused latrines. Those in use (in many cases
overflowing) are dangerous for other reasons, but not
as breeding grounds for Anopheles.

There are a few deep pools which probably contain
water during the greater part of the dry season, and
which harbour Anopheles larvae ; these require to be
filled up.

I notice that some pits are being filled with the
mixed assortment of tins and bottles removed from
houses. Broken bottles, or others, are well adapted for
filling in pits, but the use of tins is to be avoided as the
ground will certainly fall in. On these, as on other
points, the practical experience of the details gained by
Dr. Taylor will be invaluable in the next wet season.
Opposite houses, I think, some bridging of gutters

19

should be done, as otherwise the edges of the gutters
are bound to fall in.

As regards the proceedings that will be requisite
in the dry season, I can, of course, only theorise from
experience elsewhere ; combined with my observation
here of the character and lie of the ground.

The evidence seems to be clear that mosquitoes
may be expected to be more numerous in the dry
season ; because, though of the present breeding
grounds few will remain in dry weather, still there will
be other breeding places, and these will not be so
constantly disturbed or flushed by heavy rains, and,
therefore, a large proportion of larvae will reach ma-
turity.

Of the present breeding grounds, there will only
remain in the dry season some of the springs, and,
perhaps, some of the wells and pools ; the rest of the
water will then have dried up. The new places will
be mainly the streams, small and large, which remain,
possibly some of the other wells, and artificial collections
of water in tubs, etc.

Any scheme for destroying these breeding places
must take into account* (i) that abundant places must
be left for the people to get drinking water ; (2) that
places must be left in which the people can wash clothes,
etc. These two conditions will prevent any extended
application of kerosine or any odorous or poisonous
larvicide, and particularly their application to streams,
as it is mainly in expanded pools in the course of streams,
and not in isolated adjoining pools, that larvae live and
proceed to maturity.

The streams are said to contain fish, but, even if
they do not, much could not be hoped from stocking

* When the new water supply is obtained these points will not be essential.

20

them, as in such situations abundant larvae are often
present in the presence of the fish.

Two possible methods which are most obvious are
the formation of a central channel in the bed of the
stream, with larger collections of water in sufficient
numbers of places for drinking purposes, and, lower
down the stream, other places for washing, etc.

The second, which might be cheaper but less cer-
tainly effective, would be to dam up the streams so as
to obtain a sufficient head of water to flush out the whole
channel at intervals.

Either scheme would be expensive and would have
to be strong, as a rainfall of fifty inches or more in a
month of the wet season will destroy any but strong
works in the bed of these rocky streams.

I am inclined to think that the number of streams
could be reduced, and some of the smaller diverted into the
larger channels, and the number of breeding grounds thus
diminished. But on these points no positive opinion can be
given till the beds have been examined in the dry season.

Though I consider that you have already proved
the practicability of exterminating Anopheles in Sierra
Leone during the wet season, the work is at present
incomplete, even in the streets in which most work
has been done ; and, I estimate, at the present rate of
work, will still be incomplete at the end of the wet
season, when the work will be entirely changed.
During the dry season, in addition to dealing with the
new conditions which will then arise, the work already
done should be placed on a permanent footing.

In the next wet season double the men, say one
hundred, should be employed, and two Europeans for
supervision. One European, even so able and energetic
a man as Dr. Logan Taylor, barely suffices for thorough
supervision of the present work.

21

1 am aware that this will cost, apart from the
expense of supervision, over j£ioo a month instead of
the £50 to £60 which, including the cost of labour
provided locally, is now spent; but it will be better
for one place to be done well, and that a difficult one
to deal with, than that partial measures be attempted
in many places.

The experiment is being so closely watched and
criticized, that failure, or only doubtful success, would
be a disaster.

I think, therefore, that it will be more to the true
interests of West African hygiene for attention and
money to be concentrated on Sierra Leone.*

In this I would make one exception, Sekondi.
This new town will, as the terminus of the railway,
be one of the most important places on the Coast.

The European work in connection with the railway
has not only increased the actual breeding grounds, but
by means of trenches Anopheles are being conveyed
from a distance through the European settlement.
No plan seems to be followed in the erection of houses,
and, generally speaking, European work already done
has complicated matters, and will cause much increased
expense in making reasonably healthy what could easily
have been from the first a model settlement.f

I think it would be advisable to attempt to obtain
in Sierra Leone some numerical estimate of the present
prevalence of malaria, and for this purpose suggest as
the most convenient the estimation of the proportion of
children with splenic enlargement at fixed ages, say
between one and two years of age, as, up to two or
three years, reliable statements as to the age of children

* There is no fear that our efforts will be abandoned before we have done as
much as we conceive it our duty to do. — R. Ross.

-f- His Excellency, Major Nathan, informed me that he will deal with Sekondi
very shortly. — R. Ross.

22

can generally be obtained. As a check on this method,
Barbadians in the West India regiment who have not
been previously exposed to malaria, and consequently
are highly susceptible, should be examined. In them
malarial infection is indicated by malarial fever. The
length of residence in Sierra Leone requisite for malarial
infection in the Barbadians will then give an indication
of the present liability to infection.*

In conclusion, I wish to express my thanks to you
personally, and to the Liverpool School of Tropical
Medicine, for the opportunity afforded me of seeing
the first real British practical application of the principles
you have elucidated.

I am

Yours very sincerely

C. W. DANIELS, M.B.

London School of Tropical Medicine

* In order to guard against misapprehensions, it is advisable to state here that
we are not now undertaking to prove over again that mosquitoes carry malaria.
This fact was fully established long ago. Our present intention is simply to give
an object lesson in the manner of ridding tropical towns of mosquitoes by drainage
and cleaning up. We are prepared to spend a large sum of money for this
purpose 5 but we are not prepared to continue the work for ever. The work —
especially the drainage and collection of rubbish — properly belong* to the local
authorities. If they choose to continue our efforts, then we can confidently promise
that the mosquito-borne disease in Freetown will be, ultimately, very materially
reduced. If, however, they discontinue them — if they allow the town to sink back
into the condition it was in when we arrived — then I can only say that the
mosquito-borne disease will remain. It is for them to choose. I may add,
however, that I have no doubt that the former course will be the one adopted.

R. Ross

Publications of the
Liverpool School of Tropical Medicine

MEMOIR I

Instructions for the Prevention of Malarial Fever, for the use of
Residents in Malarious Places. Giving a short account of the disease and
the modes of prevention. 8oooth. Price 2s. 8°. University Press of Liverpool.

New and much enlarged edition, by Major R. Ross, F.R.C.S., D.P.H., F.R.S.,

Walter Myers Lecturer in Tropical Medicine — Forthcoming.

MEMOIR II

Report of the Malaria Expedition to Sierra Leone (1899). By
Ronald Ross, D.P.H., M.R.C.S., H. E. Annett, M.B., D.P.H., and E. E. Austen.
Being a full account of the first expedition of the School, and containing besides
much matter relating to the parasites of malaria, to the gnats which carry them,
and embodying some previous observations of Major Ross in India. Illustrated by
four maps and five full-page collotypes. Quarto. Price 10s. 6d. University Press
of Liverpool.

Note. — As only a few copies of this important work are left in stock, and as the plates
cannot be renewed, the price of the remaining copies has been raised to two guineas.

MEMOIR III

Report of the Malaria Expedition to Nigeria (1900), by H. E. Annett,
M.D., D.P.H., J. Everett Dutton, M.B., B.Ch., and J. H. Elliott, M.D. Part I.
Malarial Fever, etc. Giving a full account of the expedition, with numerous views
in the text, charts, maps and two plates, and containing much matter of general
importance. Quarto. Price 7s. 6d. University Press of Liverpool.

MEMOIR IV

Report of the Malaria Expedition to Nigeria (1900), by the same
authors. Part II. Filariasis. Containing many new observations upon Filariae
of Birds, with numerous illustrations and nineteen plates, five of which are coloured
and give the microscopical anatomy of the head of Anopheles costalis (by Dr. Dutton).
Quarto. Price 10s. 6d. University Press of Liverpool.

MEMOIR V, PART i

First Progress Report of the Campaign against Mosquitoes in
Sierra Leone (19OI), by Major R. Ross, F.R.C.S., D.P.H., F.R.S., dated 15th
October, 1901, giving details of the commencement of the Campaign, with a
letter from Dr. Daniels regarding the results arrived at to date. 8°. Price is.
University Press of Liverpool.

Note. — Succeeding parts of this Memoir will contain descriptions of the further progress of the
campaign in Sierra Leone and elsewhere.

MEMOIR VI

Mosquito Brigades, and How to Organize Them, by Major R.
Ross, F.R.C.S., D.P.H., F.R.S., containing full details regarding the mode of
starting a campaign against mosquitoes, how to conduct the work, and where to
attempt it ; with other matter relating to the subject. 8°. Price 3s. George
Philip & Son, 32 Fleet Street, London ; and

MEMOIR VII

Report of the Yellow Fever Expedition to Para' (1900), by H. E.

Durham, M.D., and the late Walter Myers, M.B. (Dr. Walter Myers died of

Yellow Fever whilst serving on this expedition.) Quarto. Price 10s. 6d.
University Press of Liverpool. (In the Press.)

MISCELLANEOUS

Malaria and Mosquitoes. A discourse delivered at the Royal Institution
of Great Britain by Major R. Ross, D.P.H., M.R.C.S., 1900 (printed by permission
of the Institution), giving a full history of the solution of the malaria problem.

/

Notes on Sanitary Conditions obtaining in Para, by The Yellow
Fever Expedition.

All of the above, except Memoir VI, to be had from the Honorary Secretary to
the Liverpool School of Tropical Medicine, Bio Exchange Buildings, Liverpool.

PRINTED BY DONALD FRASER, 37, HANOVER STREET, LIVERPOOL

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