CHAPTER VII._Climate and Health in Hot Countries and the Outlines of Tropical Climatology A Popular Treatise on Personal Hygiene in the Hotter Parts of the World, and on the Climates That Will Be Met Within Them.

On the Prevention of Malaria.

“Fever,” _i.e._, malaria, is responsible for so large a share of the

sickness peculiar to tropical countries that the subject of its

prevention requires especial and separate consideration. Up to a few

years ago the causation of malaria was a complete mystery. We had known

for some score of years or more that the disease was due to the presence

of certain minute animalcules in the blood, but as to how they got

there, or the manner in which they passed from man to man, we had not

the remotest idea. There was a general opinion that the seeds of the

disease were carried by the air in the form of what was pretentiously

spoken of as a miasma--a formidable word which served well enough to

hide from the profane vulgar the fact that no one could define, or in

fact had the vaguest notion as to what a miasma might be. It was also

popularly known in many parts of the world that miasmata found great

difficulty in getting through a mosquito net; but by the majority of the

profession these traditions were looked upon as laic fables, unworthy of

scientific attention, though there were not wanting observant

practitioners of tropical medicine who were willing to admit the

efficacy of the protection afforded by a mosquito net, and who even

attempted to account for the fact by all sorts of lame physical

explanations, barring only the simple one that a mosquito net serves

very fairly the purpose for which it is designed, viz., of keeping out

mosquitoes. The condensed moisture of the dew on the fluff of the meshes

in some way attracting the germs or dissolving some assumedly gaseous

emanation, was a favourite so-called explanation, and was, I believe,

that adopted by the late Prof. Maclean, of Netley, who in his lectures

was always careful to impress upon us the protection afforded by

mosquito nets, as a well-established, though ill-understood, fact.

This was before the date at which the French military surgeon, Laveran,

discovered the fact that malaria was due to the presence in the blood of

certain animal parasites (_Protozoa_), and although this discovery was

made in 1880, it was many years before its truth was accepted by the

general body of the medical profession, who have somehow always

exhibited a curious reluctance to admit the harmfulness of animal

parasites.

Some years later Sir Patrick Manson, F.R.S., then a hard-working doctor

in practice in China, made the remarkable discovery that the blood-worm

disease, which is very common in those parts, was conveyed from man to

man by the agency of mosquitoes; and as the parasitic origin of malarial

fever became more and more firmly established, the idea suggested itself

to him that this disease, too, might very well be transmitted by the

intervention of the same insects.

At this time Sir Patrick had left China, to work harder than ever in

London, so that he was unable to personally test the truth of his

surmise, which he, however, communicated to Major Ronald Ross, I.M.S.,

who after prolonged work, was able to establish the truth of Manson’s

suggestion, which was a remarkable instance of the value of imagination

in science. Almost immediately after Rossi’s work was confirmed and

amplified by Prof. Grassi, of Rome, and by several other naturalists,

and the fact that malarial diseases are communicated by the agency of

mosquitoes, and can be carried from man to man in no other manner, is

now absolutely established. Medical science has commonly to accept, as a

working theory, whatever hypothesis of the causation of disease may

appear most tenable, but in the present case there is no room for doubt,

and, like the protective power of vaccination, the carriage of malaria

by mosquitoes only, may be taken as one of the few absolutely proven

facts of medicine.

In saying as much, it is not implied that the reader may not on his

travels meet with medical men sceptical or hostile to this theory, but

this is because the training required to appreciate the cogency of the

facts adduced in proof is that, not of a medical man, but of a

naturalist, and though the profession of medicine numbers in its ranks

many distinguished naturalists, it is quite possible to gain the highest

qualifications without acquiring any knowledge of zoology sufficient to

render the student capable of really forming an opinion on such a point;

for, as a matter of fact, the five years of medical training are so

overburdened with absolutely necessary medical subjects, that any

critical knowledge of the associated subjects of chemistry, physics, and

biology must needs be left to the after years of those to whom good

fortune affords sufficient leisure to admit of their attacking the

fringe of these great subjects when they are no longer _in statu

pupilaris_. Hence, especially among the older hands, there are numbers

of medical men who would regard the above statements as premature, but

the reader will find it difficult to find any naturalist who entertains

any doubts on the subject. Many details undoubtedly remain to be worked

out, but the broad data may be taken as absolute facts, of a character

that future investigations can only amplify.

These facts may be shortly stated as follows:--

(1) Malarial fevers are caused by the presence in the blood of minute

animal parasites. There are several species of these, corresponding to

the various types of fever; but the life-history of all is broadly the

same.

(2) These animalcules multiply in the blood, and when they have become

sufficiently numerous, determine an attack of fever, but while in this

stage cannot pass from the blood of one human being to another, except

by the somewhat difficult vivisectional experiment of injecting the

living blood of an infected person into the vessels of a healthy

subject, a process which cannot occur in Nature.

(3) Large numbers of the malaria animalcules are destroyed by what may

be called the vital powers of the patient’s blood, and the question

whether an untreated case of malaria dies or recovers, depends on the

outcome of the struggle between the parasites and the vital forces of

their host.

(4) The process of multiplication of the parasites within the human body

is by simple division, or non-sexual breeding of the single cell of

which each parasite consists; but by a well-known law of the

life-history of this class of animalcules this method of multiplication

cannot continue indefinitely without the intervention of a period of

sexual multiplication; and this can not occur within the human subject

under any circumstances, but only in the bodies of certain species of

mosquitoes; so that the disease always tends to wear itself out,

provided the strength of the patient holds out sufficiently long; and

the parasites are unable to find their way into the blood of other human

beings by natural processes, unless mosquitoes of certain special

species be present.

(5) If, however, a human being infected with malaria be bitten by a

mosquito of the appropriate sort, the parasites, sucked into the stomach

of the mosquito along with its meal of blood, undergo further

development into distinct male and female animalcules, whose union gives

birth to myriads of germs which, although incapable of further

multiplication within the organism of the insect, find their way into

its salivary glands, which are the organs in which the irritating poison

of the mosquito is elaborated, and so are necessarily inoculated into

the tissues of any human being whom the mosquito may bite, with the

result that a new victim becomes infected, and the chain of events

commences anew.

(6) The malarial parasites can exist in the mosquito only within certain

limits of temperature, and hence the disease is not found in countries

where the maximum summer temperature is less than 76° F., or in places

so hot that the temperature rises above 86° F. for any length of time,

and the comparative healthiness of many hot continental climates is due

to the fortunate circumstance that a period of excessive dry heat

follows immediately on the cold season.

In considering the measures of prevention detailed below, it must be

remembered that their importance is enhanced by the fact that not only

malaria, but also the blood-worm disease already alluded to, or

filariasis, and yellow fever, have also been shown to require the

intervention of mosquitoes for their transmission from man to man, and

that although not carried by mosquitoes, the germs of sleeping sickness

are also probably conveyed by a winged insect, so that many of the

measures detailed below will have a certain value also in the prevention

of the last-mentioned disease.

Thus for the maintenance of malarial fever the co-existence of three

animal organisms are essential, viz., of man, the mosquito, and the

malarial protozoon; and it is obvious that even the temporary banishment

of either of the three from any given locality will necessarily put an

end to all possibility of the occurrence of fever; for man can be

infected only by the mosquito, and the mosquito by man, and the presence

of both of the others is necessary for the maintenance of the species

for the parasite.

For the proper contrivance, then, of measures of prevention it is

essential that we should be well acquainted with the life-history of our

two partners in this curious cycle of development, and as that of the

parasite has already been sufficiently described for our purposes, it

remains only to describe the leading parts of the life-history of the

mosquito. Mosquitoes, or, as they are called in England, gnats, are

small two-winged insects whose appearance is quite familiar to most

people, though midges so closely resembles them, in general appearance,

that they are commonly confused with them, but mosquitoes may be easily

distinguished by their possessing a long, trunk-like proboscis which is

wanting in the midge, as well as by the fact that, if examined with a

strong magnifier, it will be seen that their wings and the greater part

of their surface are covered with minute, downy scales exactly like

those of butterflies, while midges are quite devoid of any such

covering. The males carry a pair of beautiful plume-like feelers, while

those of the females, though quite as long, show only a few

inconspicuous hairs.

Over five hundred species of mosquito have been described; and, as might

be expected, their habits vary to some extent; but, speaking generally,

they are mainly twilight and nocturnal insects which remain hidden in

sheltered places during the day, and come forth to feed and disport

themselves in the open at dusk. Owing to the peculiar structure of their

mouth-parts, which consist of a long, delicate tube, supported in the

midst of a group of lancets, they are incapable of taking solid food,

and subsist almost entirely on the juices of living plants and animals,

which are sucked up by means of the tube which is introduced into a

puncture made by the lancets. With one or two doubtful exceptions, the

males of all species live entirely upon the juices of plants, but the

females of perhaps the majority of species are not content with so

simple a diet, and attack animals of all sorts, puncturing the skin and

filling themselves with blood till they are scarce able to fly. No

animal is safe from their attacks, and improbable though it may appear,

it is recorded, on the authority of a skilled naturalist, that young

fish are killed in large numbers by the crowds of mosquitoes which

pounce on them as they show their heads and backs at the surface of the

water.

[Illustration: FIG. 6.--Various forms of Mosquito Eggs. (1) Egg-boat of

_Culex_, seen from above; (2) the same, side view (after Sambon); (3)

separate _Culex_ eggs; (4) eggs of _Panoplites_ (after Daniels); (5)

eggs of _Stegomyia_; (6) the same more highly magnified (after

Theobald); (7) groups of _Anopheles_ eggs as they float on the water

(after Sambon); (8) egg of _Anopheles maculipennis_, showing lateral

floats, seen from above, × 30 diams.; (9) the same, viewed laterally

(after Nuttall).]

With the exception of the fleas and ticks, no insects are so admirably

adapted for the conveyance of disease from one animal to another by

inoculation; and owing to their enormous numbers, and their capability

of flight, their powers of mischief must be far greater than those of

either of these other pests. When biting an animal, the mosquito injects

into its tissues a fluid specially secreted within its body, which being

of an irritating character causes a congestion of blood round the

puncture, whereby the insect is secured a full and ample feed of blood.

The early life of the mosquito is passed in water, on the surface of

which the eggs are laid by the female flying insects. These eggs are of

various forms, but are all provided with some arrangement to secure

their floating on the surface of the water. In many species they are

glued together by their sides so as to form rafts consisting of some

hundreds of eggs, while in others, and notably in the special sorts that

carry malaria, they are laid separately and float on their sides. In a

few rare cases they may be laid on dry surfaces, in situations that

will be flooded during the rains. This is notably the case occasionally

with the form that carries yellow fever; but for practical purposes it

may be considered that the eggs can only be laid on water, and in any

case, when the young insects are hatched out, it must needs be into

water, as at that stage of their existence they are purely aquatic

organisms, and live but a short time if removed from the water. In spite

of this they are air-breathers, and in the anatomy of their arrangements

for obtaining air, present a curious resemblance to the type of

submarine boat that gets its air by means of a small tube reaching just

above the surface of the water. The young mosquitoes, or larvæ, are

small, wormlike animals, which may often be seen wriggling about

vigorously in water, and are especially common, in warm weather, in

water standing in small stagnant pools, broken crockery, old tins, and

so forth.

When full grown they are about a quarter of an inch in length, and vary

in colour from bright green, through brown to black. Two principal forms

may easily be distinguished by the difference between the structure of

their breathing organs. The first and commonest kind, of which the

common English gnat (_Culex pipiens, L._) is a good example, has a long

breathing tube projecting from the back close to the tail, so that it

looks much as if the hinder part of the body were forked.

[Illustration: FIG. 7.--Larvæ and pupa of Culex mosquitoes, as seen when

viewed from the side of a tumbler or other transparent vessel of water.

Drawn from a photograph of the living insects.]

As will be seen from the above illustration, only the tip of the

breathing tube is kept at the surface of the water, while the body and

head hang down into it in a slanting position, so that the head is the

most deeply immersed portion of the insect. In the other kind there is

practically no breathing tube, the air-vessels opening almost flush with

the surface, though in the same part of the body; and hence, in order to

keep these openings at the surface, the larvæ must needs lie

horizontally at the surface, looking much like a small blackened straw,

and on closer inspection are seen to have an outline not unlike the

ornamental keyhole plates often seen in old-fashioned furniture. They

generally lie with their tails supported against some solid object,

such as the side of the saucer in which they have been placed for

observation.

[Illustration: _PLATE I._

Living _Anopheles_ larvæ. Photographed by Mr. T. H. ROYLE, of Rosa.]

Owing to their being confused with the line of optical contact of air

and water, and the latter being raised by adhesion into curves over

their backs, they do not come out as clearly in the photograph as in a

drawing, but they are, nevertheless, sufficiently clearly shown for easy

recognition, a matter of some importance, as these are the larvæ of the

sub-family _Anophelinæ_, to which belong all the mosquitoes that are

concerned in carrying malaria, besides which they are the commonest

carriers of blood-worms. The mosquito, however, that conveys yellow

fever (_Stegomyia_) belongs to the Culex sub-family.

[Illustration: FIG. 8.--(1) Larva commonly found in jhils and tanks

(probably of _Myzorrhynchus sinensis_.); (2) frontal bristles of the

same; (3) abdominal palmate tuft; (4) separate leaflet of palmate tuft.]

For any one possessing a microscope these larvæ form most fascinating

examples of “pond-life,” as many species, especially when young, are

transparent enough to enable one to follow the entire mechanism of their

internal organs; but a great deal of interest can be made out with a

simple hand-lens.

On the back of each of the rings of the abdomen, or hindmost division of

the body, of the Anopheles larvæ may be made out a pair of structures

formed like minute palm leaves, the function of which appears to be that

of keeping the little creature flush with the surface of the water.

One of these larvæ, magnified about twenty times, with these structures

and certain peculiar hairs on the front of the head, which are of value

in distinguishing one species from another, more highly magnified, is

figured on the preceding page. By the aid of these illustrations the

reader should have no difficulty in recognising these organisms when he

meets with them. When disturbed, they dart backwards and seek refuge

among the _débris_ at the bottom, but cannot remain there long, and soon

resume their resting position on the surface.

The larvæ of many species are said to be carnivorous, and even

cannibalistic, though I cannot say I have ever observed this personally,

and in any case their main provision is found in the minute vegetable

organisms which are abundant in the sites where they are common; the

Culicine larvæ confining themselves mainly to those that are found

completely immersed, while the young Anopheles browses on those floating

on the surface, keeping its head screwed round, a full half-turn, so as

to bring the mouth uppermost. The abrupt way in which this action is

performed and reversed is extremely quaint, so that, as a writer

remarks, one is rather surprised at its not being accompanied by an

audible click.

The duration of the period of larval existence depends on the

temperature of the water and on the abundance or scarcity of food. When

first hatched out from the egg, the larvæ are barely visible to the

naked eye, whereas when full grown they contain within themselves the

entire material of the adult flying insect. Once full-grown, the weather

being favourable, they change into “nymphs” or pupæ, not unlike small

tadpoles in form, the head and thorax being enclosed in an almost

spherical envelope, to which is appended a sort of tail, formed by the

abdomen, which is usually kept folded under the body, as shown in the

figure below. In this stage the animal breathes through a pair of horns

springing from the back of the thorax. The mouth is completely closed,

so that the pupa is incapable of feeding, but is in no sense quiescent,

as it is capable of lively movements and tries to elude capture almost

as briskly as the larva. After a sufficient time has elapsed for the

completion of the extraordinary anatomical changes that convert the

larva into the adult insect, the pupa-case bursts along the back, and

the perfect gnat gradually disentangles itself from its temporary home,

and flies away, very shortly to reinitiate the cycle of events by laying

a fresh batch of eggs. As has already been remarked, the time required

to complete these changes varies greatly in different species and under

varying environments, of which climate is the most important factor, but

under moderately favourable conditions the time required is a fortnight

or three weeks, the greater part of which is passed as a larva. In

countries where water freezes during winter for any length of time, all

larvæ that have not completed their metamorphosis by the end of autumn,

must necessarily perish; and the continuity of the species is maintained

entirely by the survival of pregnant females that hide themselves in

warm corners and pass the winter in a truly hybernating or dormant

condition. Further south, both males and females hybernate, and the

dormancy is so much less pronounced that the insects are often tempted

to issue from their hiding places on exceptionally warm days. In such

climates, which include Italy and most of the sub-tropical zone, the

species finds an additional string for its bow in the survival of larvæ,

which, though they cannot be said to hybernate in the strict sense of

the term, being always lively and alert in their movements, are yet

incapable of growing, and appear to remain at whatever size they may

have previously attained until the return of warmer weather. Quite

recently Dr. Bancroft, of Queensland, has discovered that in some

species these wintering larvæ can give birth to small broods of young

larvæ, so that in such cases the bow has no less than three strings.

Further south again, in truly tropical climates, breeding goes on all

the year round.

[Illustration: FIG. 9.--Larva and Nymph of _Anopheles_, to show habitual

resting position. The head of the larva is shown looking up, as when

feeding.]

No adult mosquito can stand the direct rays of the sun, and hence all of

them have to seek the shelter of houses, trees, or some such protection,

during the heat of the day; moreover, with very few exceptions, they are

nocturnal or twilight insects, so that there is comparatively little

danger of being bitten during the hours of daylight. For the majority of

species too, extreme atmospheric heat has much the same effect as great

cold, so that during periods of intensely hot, dry weather the number of

species to be met with in a state of activity is very small, and

fortunately those that convey malaria are not amongst the number; but on

the other hand, the one or two sorts that possess this tolerance are so

enormously prolific that their numbers far exceed those of all other

species combined.

Another point of importance is that, for practical purposes, mosquitoes

cannot fly far, and hence never wander far from the puddle on which they

were born. Being tolerably long-lived insects, it is of course possible

for them to slowly spread amongst trees or bushes for considerable

distances, a few straying further and further away every night from the

place of their birth, but the number that can travel in this way for any

considerable distance, is so small as to be scarcely worth

consideration; and any considerable expanse of bare, open country is

practically impassable to them.

Mosquitoes are most active during the periods of twilight, and

especially in the evening, at which time they quit the shelter in which

they have dozed away the day, and come out into the open to seek their

food, remaining outside for the most part throughout the night, though

the females of those species that attack man and animals, it is needless

to say, will find their way back into houses in search of their

favourite food. As soon, however, as the sun has got well above the

horizon they may be observed trooping back into the house, and if a

window be closed it is very amusing to watch the numbers that will

alight on the glass at this time of the day, and their efforts to find a

way through the obstruction. The special importance of keeping all means

of entry closed at this particular hour can therefore easily be

understood, though in ordinary tropical practice, it is the very time at

which every door and window is habitually thrown open.

Mosquitoes are found all over the world, it being a great mistake to

imagine that they are confined to tropical climates. Some score of

species are to be found in England, and though in high latitudes they

cease to be dangerous as carriers of disease, there are perhaps no

localities where they are so numerous and troublesome as certain parts

of the North American Continent, and in Scandinavia, close up to the

Frigid Zone.

Almost any collection of water will serve as a nursery for the larvæ,

unless indeed, there be a decidedly strong current; but the situations

taken by preference during the breeding season are small stagnant pools

and domestic collections of water, such as small tanks, broken crockery,

empty tins, &c.; while wintering larvæ prefer the larger ponds and

marshes which are permanent throughout the cold weather, and especially

select those in which there is sufficient vegetation, reaching to the

surface of the water, to afford cover and protection from their numerous

enemies. Practically speaking, wintering larvæ will never be found in

tanks or ponds devoid of fairly robust vegetation, and it may easily be

understood from this fact that the clearing away of reeds, grasses, and

weeds of all sorts during the cold weather from all such collections of

water which may be found near an inhabited site is a most important

sanitary measure. Some species prefer the fairly clean water of marshes

and ponds, while others luxuriate in the dilute sewage of the domestic

waste water, but it would occupy too much space to go into any detail on

this subject, and all that the sanitary amateur need remember in this

connection, is that any and every collection of water, capable of

standing for ten days or a fortnight, should be regarded as dangerous to

health in any country where malaria is known to exist.

For our purposes, it will suffice for the reader to understand the

general characteristics of three sorts of mosquitoes. First, there are

the common _Culex_ mosquitoes, which are, almost everywhere, far more

common than the others. They are usually of a dull grey colour, and with

very few exceptions, their wings are quite plain and free from spots. As

will be seen from the photographs in the accompanying plate, they sit in

rather a humped-up position, and the proboscis is obviously much thinner

than the body, its appendages, or palps, being held apart from it.

Mosquitoes of this sort cannot convey human malaria, though they are

instrumental in conveying a similar disease for certain animals. They

are to be found, in greater or less numbers, throughout the year.

The second sort is the _Stegomyia_, which is the genus concerned in the

conveyance of yellow fever. These mosquitoes are seldom to be seen

except during the rains, and rest in much the same position as the

_Culices_, which they resemble closely in form. Their wings are never

spotted, and almost all are small insects clothed with jetty-black

scales, picked out with an ornamentation of dazzling white lines on the

body and spots on the abdomen and legs.

[Illustration: _PLATE II._

Photographs of living mosquitoes. Above, ♂ and ♀ _Culex_ mosquitoes in

profile; in the middle, ventral aspects of the same; and beneath, ♀ and

♂ _Anopheles_ mosquitoes. About twice natural size.]

The third, or _Anopheles_, sub-family is that concerned in the

transmission of human malaria, and, as may be seen by comparing the two

lower photographs of the plate with the upper ones, can easily be

recognised by their characteristic form and attitude. In these

mosquitoes the feelers are long and thick in both sexes, and as they are

held habitually in contact with the proboscis, these together appear to

the naked eye as a prolongation of the body as thick, or thicker, than

the abdomen. Moreover, except in a few species, their position, when

resting, forms a singular contrast to that of the _Culices_, the whole

body and proboscis being held in one straight line, with the abdomen

raised from, and the proboscis pointed almost vertically at the surface

on which they rest, and almost touching it with its point, as if they

were preparing to drive the latter into it; so that, viewed with the

naked eye, they look much like minute black thorns, stuck into the

surface on which they are sitting. On closer examination, it will be

seen that the wings are not plain, but spotted (the number of

plain-winged species being unimportant).

[Illustration: FIG. 10.--Wings of various sorts of _Anopheles_

mosquitoes, much magnified, to show the arrangement of the dark and

light scales which form the characteristic spots.]

The appearance of spotting is usually produced by alternate lengths of

the veins of the wings being coloured in finely contrasted dark brown or

black, and white or yellow, and varies, of course, in detail in

different species, but the above figures of the wings of some of the

commoner Indian forms will give an idea of the general effect, as seen

under a moderate magnification, for though the spots are quite visible

to the naked eye, it requires a fairly powerful hand lens to make out

the details properly.

Like the _Stegomyiæ_, the _Anophelinæ_ are only common during the rains,

but stray specimens will be met with for a month or two afterwards; and

though they practically disappear during cold weather, a few may be

generally met with during the hot dry months of continental hot

climates.

From what has been said, it follows that the prevalence of malaria, like

that of mosquitoes, must necessarily be seasonal. The survival of the

malarial parasite at those times of the year when mosquitoes are scarce

or absent, is maintained by the persistence of considerable numbers in a

latent condition, in the persons of human beings who have been

imperfectly cured of an attack of malaria.

Cases of this sort, which have either been never treated at all, or in

which the administration of quinine has been stopped too soon, are

extremely common in all malaria-stricken communities, and such persons

are always liable to relapses if they are brought below _par_ by any

depressing influence, such as chill, too great exposure to the sun, or

the incidence of injuries, or of other diseases.

During such periods the latent parasites, which have been perhaps for

months lying hidden in the internal organs, will reappear in the blood

in large numbers, and there are always a sufficient number of such cases

of relapse persisting through the naturally malaria-free season, to

suffice to infect the early broods of mosquitoes that come to maturity

with the advent of the rains.

This shows that the curing of all cases of malaria is matter by no means

confined to the interests of the patient himself, but is of great

importance to the entire community of which he is a member; for, despite

the fact that the disease is only indirectly transferable through the

agency of the mosquito, a case of malaria is as great a danger to his

fellow-men as one of any other infectious disease, and should, as far as

possible, be dealt with in the same way; only the problem of isolation

is in this case easier than usual, as it suffices to prevent mosquitoes

getting access to the sick person; and in a properly fitted

mosquito-proof house or hospital, malaria cases may quite safely be

allowed to mix freely with the healthy, as well as with persons affected

with other diseases.

Relapses in persons chronically infected with malaria may occur at any

time of the year, but the fresh infections, which always form the bulk

of the cases met with, can only happen as the result of a tolerably

recent bite by an infected mosquito; and as about a couple of weeks are

required for the maturing of the parasite within the insect, and a

further period of incubation is necessary within the human subject

before the parasites attain sufficient numbers to produce a definite

constitutional reaction, fever does not as a rule commence in earnest

until some three weeks or a month after the break of the wet season.

Once the process is started, infected mosquitoes and malaria-stricken

men increase in numbers rapidly, and as numbers of infected mosquitoes

survive for a considerable period after the cessation of the breeding

season, the prevalence of malaria continues until the advent of cold

weather puts a period to the possibility of the survival of the parasite

within the insect organism. Hence it is generally quite possible to give

a fair idea of the monthly distribution of rainfall in any warm climate

from the returns of sickness and mortality, and _vice versâ_.

The natural history of the living organisms that are concerned in the

propagation of malaria has been described with some detail, as suitable

measures for the prevention of the disease must needs be based on a

fairly competent knowledge of the subject, and is the more necessary as

it is hardly possible to give any “rule of thumb” directions; because

the circumstances on which the prevalence of malaria depends vary so

greatly in different localities that, to ensure success, our operations

must necessarily be modified in each case to meet local conditions.

In the following remarks, however, it is not proposed to deal with the

question of prevention on a large and public scale, but only with such

as can be adopted as measures of individual and personal hygiene, as the

larger question of provincial and municipal anti-malarial sanitation

cannot be adequately dealt with in a short treatise like the present.

Keeping always in view the just described data of the life history of

the malarial parasite and of its temporary host, the mosquito, it is

obvious that our measures of protection must be based on one or more of

the following plans of action, any one of which, could it be carried to

complete success, would suffice to “stamp out” the disease. These

measures are:--

(1) To destroy the mosquitoes.

(2) To prevent mosquitoes biting man.

(3) To prevent mosquitoes from becoming infected, by isolating all cases

of malaria in man.

In practice, however, it is extremely rare that anything like complete

success can be attained on either of the three above indicated lines of

action, especially as concerns the second and third methods, and though

here and there localities may be met with in which the breeding places

for mosquitoes are so circumscribed and easily dealt with as to render

the actual extermination of mosquitoes practicable, in by far the

majority of cases we must be content with a partial success all along

the line, by adopting such measures as may be locally most practicable,

based on any or all three of the above principles of action.

In the case, for example, of habitations placed in the midst of canal

irrigation where ample and efficient subsoil drainage is impossible or

too expensive, the attempt to destroy mosquitoes can be little better

than a waste of time and money; for under such conditions the breeding

places are so numerous, and appear so constantly in new and unexpected

situations, as to defeat the utmost vigilance; and the thorough

protection of all habitations against the invasion of mosquitoes, and

the careful treatment of all cases with quinine, is all that can be

done. On the other hand, in an exceptional case, such as that of the

town of Ismailia in Egypt, where the rainfall is practically _nil_, and

the breeding places all of artificial origin, the practical

extermination of mosquitoes may be so easy a matter as to be effected at

a small expense in a single year, with the immediate result of reducing

the cases of malaria to a tithe of their previous numbers.

Measures of the first class, _i.e._, the extermination or diminution of

the numbers of mosquitoes, can often be undertaken with considerable

success by private individuals, the possibilities of success varying, of

course, with the extent of the area directly or indirectly under his

control.

The resident of a closely inhabited town can, it is needless to say, do

no more than contribute his personal mite to the general welfare in this

matter, with little chance of reaping much benefit unless his neighbours

follow his example; but with the exception of diplomatic officials and

merchants residing in places under oriental rule, where the safety of

life and property are too badly secured to admit of their living outside

town limits, it is rare for any European to be so situated, as in most

of our colonies and dependencies the European quarter of the town

consists of widely separated villas each surrounded with a garden of

some size, with generally a small hamlet of dwellings for native

servants and dependents included within its boundaries. In addition to

this, there are often open spaces, of considerable extent, between the

various “compounds” which, though not directly under one’s control, are

so far “no man’s land” that no one will interfere with any one employing

on them any of the measures required for anti-malarial sanitation, while

the most litigious municipal council is hardly likely to object to the

sprinkling of a little paraffin on the roadside puddles. In this way it

will generally be possible to effect a good deal within a radius of

three or four hundred yards of one’s dwelling, and actual experience has

shown me that if all breeding places within such limits can be rendered

harmless the number of stragglers that will stray across from places

beyond will be too small to be seriously troublesome.

In devising measures for the destruction of mosquitoes it is obvious

that while they may be attacked either in the aquatic or aerial stages

of their existence, the easily localised larvæ and pupæ will be far more

easily dealt with than the elusive flying insect, and it will be

therefore best to devote most attention to the destruction of the

former.

There are two principal methods of dealing with the insects during their

aquatic stage, _i.e._ (1) by doing away with their breeding places; (2)

by poisoning them. Of the two it is clear that the former method is,

where practicable, the more valuable, as in nearly all cases its effects

are more or less permanent. With either object in view, however, the

first step is to seek out the breeding places.

As a preliminary measure, all domestic rubbish capable of holding water,

such as disused flower-pots, empty tins, &c., should be carefully sought

out and destroyed or disposed of by throwing into some depression of the

soil which it is desired to fill in. Next, the entire surface should be

carefully inspected after a brisk shower of rain, and all such puddles

as are of manageable dimensions carefully filled in and levelled.

The amount of labour that can be profitably afforded in work of this

sort will depend a great deal on the probable duration of one’s stay in

a place; as temporary residents, such as government officials, will find

it much cheaper to employ temporary measures, such as the use of

paraffin; while in the case of merchants and other permanent residents,

the expenditure of a considerable sum on permanent measures will be more

remunerative in the long run. The great difficulty often lies in finding

spoil wherewith to fill in the depressions, as unless care be exercised,

the only result will be to shift the site of the puddle. Sometimes,

however, a bank of earth surrounds the compound by way of a hedge; and

as in a level country the existence of such an obstruction to surface

drainage is most objectionable such banks should always, if possible, be

removed and a hedge of wire or bamboo substituted; when the spoil can be

advantageously utilised for filling in hollows. Where no localised

elevations are to be found, the material required should be obtained by

a general very slight removal of the surface. In other cases it may be

possible to drain a depression by cutting a shallow gutter to the

nearest surface drain.

Another and very important class of breeding place consists of the

comparatively large collections of water formed by the various

reservoirs, channels, &c., constructed for obtaining and storing water

for various domestic purposes, such as wells, tanks, &c., and especially

the appliances for watering gardens. Of these the most harmful of all is

canal irrigation, which should undoubtedly be never tolerated near a

dwelling by any one valuing his health, malaria or no malaria; for the

waterlogging of the soil, that is practically inseparable from the

system, is either the exciting or predisposing cause of a variety of

diseases, many of which, such as rheumatism, consumption and cancer, are

perhaps more seriously dangerous than malaria. Sodden and waterlogged

sites are notoriously unhealthy all over the world, and chronic

ill-health is a high price to pay for a few flowers and vegetables; so

that the settler will be well advised to leave irrigated cultivation to

those who are constrained to adopt it for a livelihood, and banish it

from his own premises; as much is gained by living on a comparatively

dry site of however limited extent.

As a matter of fact, indeed, the possession of a garden of any sort is a

more than doubtful benefit in malarious places, for trees and shrubs

necessarily form lurking-places for mosquitoes; and even with the

greatest care, it is difficult to carry out the necessary watering of

the plants without giving rise to puddles; while the various reservoirs,

&c., that are almost indispensable, are a constant source of danger

unless constantly and minutely supervised.

In India, for example, gardens are commonly watered from wells by means

of water lifts of various forms, which are worked either by means of

bullocks or by manual labour. In order to facilitate the distribution

of the water, masonry channels are usually constructed which carry the

water from the well head to all parts of the garden, and as the lift

cannot conveniently be worked continuously, a number of small tanks are

arranged along the line of channels wherein water is stored, so that it

can be dipped out and distributed by means of an ordinary watering can

without the gardener ever having to go far to replenish it. Now these

small tanks are _par excellence_ the main source of supply of mosquitoes

of all species, and therefore of malaria, to the houses to which they

are appended. If, therefore, a garden be considered indispensable, all

such tanks should be carefully emptied and all deposit cleaned out at

least once a week; under which circumstances, though they will probably

swarm with larvæ by the end of the time, it is impossible for any of the

latter to complete their metamorphoses into adult insects. By far the

least objectionable plan of relieving the dust and glare of a bare

situation is the cultivation of a well-kept lawn, a few large trees

being left and the area of flower beds strictly limited, for as flooding

the grass is sure to spoil a lawn, success can only be ensured by

careful and moderate waterings at frequent intervals.

Collections of water that are too large to be done away with by filling

in or by draining, should be dealt with by oiling the water with

paraffin. There are some other agents which may be employed for the

purpose, but none of them are so cheap, efficient, and readily

obtainable. As an additional advantage, though fatal to all kinds of

insects, it is in the quantities employed, not only absolutely harmless

to vegetation, but water so treated is actually a most valuable

application, owing to its power of destroying other injurious insects.

When sprinkled on water paraffin spreads out into an extremely thin

film, so that a very small quantity will cover a considerable area. A

three-gallon tin, for example, contains enough to cover an area of 100

yards each way, though it may be a day or two before the oil reaches all

parts of such a space. It is important to remember that the cheaper and

commoner the oil, the better it is for the purpose, and the addition of

a little of common bazar _ghi_, or clarified butter, is said to make

the oil spread better and render its action more lasting, though the

writer has not personally experimented with the mixture.

In the quantities used there is no possible danger of fire, even though

wooden structures, such as the piles of bridges, be immersed in the

water, as the film is so thin that it is impossible to ignite it; a

matter one would have thought sufficiently obvious, were it not that

objections have been gravely raised to the use of paraffin on this

score.

The method of application must be varied to suit the size and situation

of the piece of water to be dealt with. Small puddles, such as those

left in the course of roadside ditches, may most economically be dealt

with by, as it were, lightly wiping over the surface with a wisp of rags

dipped in the oil; filling in being in such cases out of the question,

as to do so would be equivalent to obstructing the drainage; and it is

quite impossible to maintain an exact and uniform gradient in an

unrevetted channel.

For larger collections of water, by far the best appliance is an

ordinary gardener’s watering-pot. The oil should be applied mainly along

the windward side of the pool by a coolie, who should, if possible, walk

out some distance into the water, and should be trained to sprinkle the

oil by rapid single sweeps of the rose of the can, a few steps being

taken between each sweep, as there is no need to make the loop-shaped

areas of water sprinkled in this way continuous, as the oil will spread

laterally and join each of them together even if separated by several

yards, and no advantage whatever appears to be gained by applying the

oil thickly. In exceptional cases, such as the moats of fortifications,

where the water is enclosed within high vertical walls, a garden syringe

may be required in place of the watering can.

In situations such as the pools in canal beds, ditches, &c., the oiling

must obviously be done after each flow of water through the channel; but

in most ordinary situations, the effects of a careful oiling may be

trusted to last for at least three weeks, as, though larvæ may be

beginning to reappear by the end of that period, none of them will have

had time to complete their metamorphoses. For the destruction of

wintering larvæ, two oilings, one at the commencement, and one towards

the end of the cold season, amply suffice; and in Continental hot

climates it is needless to repeat the process during the dry hot season,

as at that time only artificial breeding places, such as garden tanks,

require attention, and these are better dealt with by periodical

emptying.

At that season indeed, the undried-up breeding places are so few and far

between that people have only themselves to thank if mosquitoes are in

evidence at all; and yet in many places there is no season of the year

when they are so numerous and tormenting. There are no remaining natural

breeding-places, and the pains of a weekly stroll round one’s premises

to ensure the emptying and cleaning out of all garden tanks,

water-vessels, &c., are all that is required to secure complete immunity

at that season of the year, but it is most difficult to induce people to

take even this trifling trouble; and the mosquitoes are likely to

flourish undisturbed until the existence of breeding places within the

premises of any person is treated by the authorities in the same way as

other dangerous nuisances; and yet these very people are the loudest in

their condemnation of the inertia of the native in sanitary matters, and

while they maintain malaria breweries on a scale in which the modest

extent of his premises forbids him to compete, inveigh against him for

starting a cholera factory on the most modest lines. The native who

refuses to avail himself of the protection against plague of a health

camp is, they admit, an impracticable fool for his pains; but the

_sahibs_ of the civil lines, whose gardens supply a large share of the

harmful mosquitoes to the neighbouring city, are merely “common-sense”

people who attach no importance to doctor’s fads and “scientific rot” of

all sorts. The native, however, has at least usually the excuse that he

is unable to read or write; and for the rest, does not pretend to be a

very highly civilised person.

Once they have emerged from the pupa case, our means of attacking

mosquitoes are comparatively feeble, and for those that habitually pass

most of their time in the open air practically _nil_.

In the case however of domestic species, which habitually shelter in

houses, a good deal can be done in this matter; and, just as in the

repression of other troublesome insects, such as fleas and bugs,

scrupulous tidiness and cleanliness is by far the most important of all

agencies. Useless, rarely dusted draperies and curtains, and untidy

collections of clothing hung about on nails and pegs, instead of being

kept in properly closed wardrobes, are the things that are mainly

responsible for attracting and sheltering mosquitoes within houses, for

they will not, if they can avoid it, remain in a well-lighted room, with

freshly colour-washed bare walls.

In the tropics, the Italian villa with its frescoed walls and minimum of

useless furniture, is the ideal that should be aimed at, and not the

elaborate lumber warehouse of an English drawing-room; which, though

comparatively harmless in our own climate, is about as well adapted for

imitation in hot countries as the coat of the Polar bear in the Zoo is

suited to our summer.

Perhaps our most effective agency in dealing with adult mosquitoes

depends on the intense objection all species of these insects entertain

to smoke.

That it is quite possible to effectually protect animals from mosquito

bites by the agency of smoke alone, has recently been conclusively shown

in the course of Mr. Power’s experiments on the prevention of horse

sickness in South Africa; but, though most semi-civilised people seem to

live comfortably enough in a smoky atmosphere, Europeans would find such

a state of things intolerable; and the plan can only be utilised to

drive mosquitoes out of houses, other methods being relied on to prevent

their re-entering. Smoke from almost any source will put mosquitoes to

flight, and if sufficiently intense will stupefy them; but certain

special materials must be burnt if it is desired to kill them outright,

and our _modus operandi_ must be varied according to the means at our

disposal, for if we can only expect to annoy the insects sufficiently to

drive them out of doors, the latter must be left open during the

fumigation; whereas, if it is proposed to kill them, all openings must

be closed as completely as possible, so that the fumes may reach the

insects in as concentrated a form as possible.

For simply driving out mosquitoes, any fuel that produces a dense smoke,

such as damp straw, will serve. Maize cobs are excellent for the

purpose, but probably the least objectionable is the burning of a little

incense (Hindustani, _Lobán_). To actually kill them, on the other hand,

it is necessary to shut up all openings as closely as possible, and to

burn certain special substances, such as sulphur, unopened chrysanthemum

flowers, the leaves of the neem tree, tobacco, &c., and the degree of

success attained will vary a good deal according to the character of the

building in which it is attempted; it being obviously extremely

difficult to secure an adequate concentration of the fumes in a very

pervious structure, like a house with a thatched roof and walls of

bamboo matting, such as is often met with in Burmah and the Malay

Archipelago. Under such circumstances, the rapid burning of a large

amount of the fumigating agent is the only way of meeting the

difficulty; and under any conditions, plain sulphur, simply ignited as a

powdered mass, or placed on the hot coals of a charcoal brazier, burns

so slowly as to be quite useless.

A few instants’ exposure to an atmosphere containing a fairly high

percentage of sulphurous acid will kill any insect, whereas they will be

merely stupefied or unaffected by prolonged exposure to a weaker mixture

of the poison. I am quite aware that sulphur has been decried as almost

useless by several observers, but this is simply because they have not

used it properly; for to secure success, something must be added to the

sulphur which will make it burn quickly, and what is wanted is, in fact,

a weak firework. In well-constructed buildings the sulphur pastiles

prescribed in the second edition of my work on the “Gnats or Mosquitoes”

answer sufficiently well, but subsequent experience has shown that the

proportion of nitre is not enough to secure a sufficiently rapid

combustion to instantly flood the air with sulphurous acid, and that

nothing short of a slow burning firework, such as a Roman candle or

Bengal light, will do this in a building roofed with tiles or thatch.

Possibly it might be advantageous to raise the proportion of sulphur;

and it is undoubtedly better to pack the material as a powder in paper

cases, than to mould it into pastiles. Proper precautions against fire

must of course be taken, but in fireworks of this sort the sparks do not

fly far, and it is quite safe to use them in any ordinary room if the

precaution be taken of placing the cases under a low shield, formed of a

sheet of corrugated iron supported on four piles of bricks.

The occasional fumigation of a dwelling in this way is a useful adjunct

to the destruction of the larvæ; and where combined with proper

wire-gauze protection, after the plan described below, may be relied

upon to secure immunity from the attacks of insects, even where measures

for the destruction of larvæ are impracticable. It has the further

advantage that it is fatal not only to mosquitoes, but also to insect

pests of all sorts, such as flies, hornets, bugs, or fleas, and even to

such more awesome foes as scorpions and centipedes, all of which delight

to share the home of the dweller in tropical climes.

Mosquitoes are always greatly attracted by draperies, especially those

of dark colour, and the fact may be utilised to trap them by means of

deep bags of black gauze (_chiffon_), the mouths of which are held open

by an oval loop of cane, or some such material. Such bags, if hung up

mouth down-wards in tempting dark corners, will usually be found

swarming with mosquitoes each morning, and the insects can easily be

killed by crumpling the bag in the hands and then shaking out the dead

insects.

By working on the above lines, especially where one has the co-operation

of neighbours, it is in all cases quite possible to materially diminish

the nuisance of mosquitoes, and under favourable circumstances to

practically extirpate them; though, in a usual way, complete success

must not be expected. In the exceptional cases where this is possible,

there is, of course, no need for the adoption of any other sort of

measures; but, in the majority of cases, an amelioration only in the

numbers of insects is all that can be attained; and it is necessary to

guard against the risk of some of the survivors becoming infected, by

the adoption of measures of the second and third classes. Of these the

second, _i.e._, the protection of man from mosquito bites, is in most

cases the most easily practicable.

A variety of ointments and applications of various sorts have been from

time to time vaunted as protectives, and the presence of certain plants,

such as the eucalyptus and the castor-oil shrub, have also been stated

to be so obnoxious to mosquitoes of all sorts that they might be trusted

to make themselves scarce wherever these plants might be found. For

these ideas there is doubtless this much foundation in fact, that most

strongly smelling bodies really are obnoxious to mosquitoes; but

unfortunately, whatever objection they may have to strong scent is not

very deeply rooted, and in default of more congenial shelter they will

settle upon either eucalyptus or castor-oil plants, and will brave even

the hated smell of paraffin to secure a good feed on the blood of a

human or animal subject. All these special applications to the skin,

too, have the further disadvantage that, though some of them are fairly

effectual for a few minutes after they have been just applied, and so

enable the user to get sleep, they leave those who are deluded into

depending upon them to fall unresisting victims, as soon as the thick of

the scent has evaporated. So that, though valuable for securing rest,

they are worse than useless from the point of view of the prevention of

malaria. With these untrustworthy exceptions, all available measures are

of a mechanical character, and consist in modifications of our housing

and clothing.

It must be remembered that during the working hours of the day there is

little chance of being attacked, at any rate in the open air, and the

same is the case in well-lighted rooms. Thus men whose work takes them

into the open air for some considerable portion of the day, or are

occupied in well-lighted offices, run much less risk than ladies, who,

when they attempt to face the hot weather at all, are too fond of

shutting themselves up in a darkened room, devoid of light or fresh air,

and filled up with hangings and other superfluities, so as to form a

perfect mosquito paradise in which the insects can fly about and bite

during the day as comfortably as during the night. With such exceptions,

there is therefore no need to modify costume to diminish the chance of

mosquito bites as long as the sun is up, or even during the twilight, as

long as one is in motion. It is when people are resting after the

evening game of golf, racquets, or tennis, that they are most commonly

attacked while awake; but the time of greatest danger is the period

passed in sleep. During the waking hours it is uncommon for a mosquito

to get the chance of an undisturbed meal by attacking the face and

hands, but she often does so by attacking the ankles, and even thick

stockings are no adequate protection. Trousers are therefore more

suitable than knickerbockers for evening wear, and should be made extra

long; so that when turned down after taking one’s evening exercise, they

thoroughly protect this very vulnerable portion of the person. A lady

can generally arrange her dress so as to protect herself, but the

ordinary costume of children is extremely dangerous, and certainly

should be modified to meet this danger during the hours when mosquitoes

are active. In the case of little boys a “sailor suit” with long

voluminous trousers meets the difficulty; and--fashion or no fashion--it

is a clear duty on the part of mothers to devise some cool but adequate

protection for the little girls. The alternative lies between doing so

and wilfully offering them as sacrifices to the god of dress by

needlessly exposing them to the danger of infection.

The low-necked, sleeveless dresses worn by ladies in the evening must,

we can well understand, be very temptingly cool wear in the climates

with which we are dealing, but are obviously extremely dangerous, as

they leave a large surface of the person exposed at the very time when

mosquitoes are most active. A dress covering these parts should be

therefore substituted, which, however, may safely be made of the

lightest materials, provided that it be so puffed or otherwise

“confectioned” as to make it difficult for a mosquito to get within

reach of the skin. Mosquitoes are always fond of collecting under

tables, as they are there sheltered from the glare of the lamps, and on

this account it is advisable for men to wear straps to their trousers

when dressing for dinner; and though the plan is a very old-fashioned

one, I have some hope that the suggestion may meet the approval of our

better halves, as, whatever its real object, the adoption of the plan

certainly gives the wearer the air of having sacrificed comfort to

appearances.

There would, however, be no need of modifying costume for indoor wear in

any way were houses properly protected against the entrance of

mosquitoes by means of suitably planned wire-gauze protection to all

openings.

The plan in question was devised by Professor A. Celli, the Principal of

the Institute of Hygiene in the University of Rome, and in Italy at

least has long passed its experimental stage; though, owing probably to

the small number of Englishmen who are familiar with the Italian

language, it appears to be practically ignored even by our specialists

on the subject.

Within a few miles of the great city of Rome there are large areas where

malaria, far more virulent than the type of disease we usually meet with

in India, is so rife that, during the malarious months, the country is

practically deserted by all but a few necessary railway officials and

caretakers. Amongst the former the mortality and invaliding used to be

so heavy that the working of the lines was a matter of the greatest

difficulty.

The majority of the peasantry, being only temporary inhabitants, live in

grass huts not a whit in advance of those of the savages of Central

Africa, and from the migratory nature of their employment, are among the

most ignorant and backward of the Italian populace, and so about the

last people likely to lend themselves to the adoption of any

“new-fangled” custom. As a matter of fact, however, the object lesson of

the advantages of the system have been so obvious that, after the first

year, there has been no difficulty in securing the eager co-operation of

the simple railway men and scarce civilised farm hands. As the system is

necessarily being very gradually introduced, there are plenty of

unprotected houses for comparison, and after personally conversing with

the inhabitants, the writer found that all who had enjoyed the benefits

of the plan were convinced of its efficacy.

It must be remembered, however, that it has been long a matter of

popular belief in the Campagna that malaria was, in some way, caused by

mosquitoes; and it is the difficulty of convincing those in high

authority of this fundamental fact that is at the root of the

indifference and inertia which oppose all attempts at amelioration in

India and in many of our colonies.

During the first two years’ experiments on the Campagna, out of 25

protected cottages, with a population of 173 persons, only 8 persons

contracted malarial fever; while in 30 unprotected cottages, having a

population of 220, only 17 escaped the disease; although the protected

and unprotected cottages were, as far as possible, paired as regards the

site, and were otherwise of a uniform plan of construction, and all

inhabited by the same class of railway subordinates.

The system is the one above all others most suited for adoption by

private persons, because it secures an almost complete immunity in spite

of the most unfavourable surroundings, and renders the user quite

independent of the sanitary lapses of his neighbours; but in spite of

this, the plan is almost ignored in our English colonies and

dependencies, though the writer has recently received an interesting

communication from a medical man practising in China who has adopted it

with signal success.

Professor Celli’s plan consists in rendering habitations impervious to

the entry of insects by closing all openings with wire gauze (mesh of

about 12 strands to the inch). All windows, as well as such doors as

only serve as such, and are not absolutely required for ingress and

exit, are permanently closed by frames covered with the gauze, and all

indispensable exterior doors are fitted with _double_ spring doors of

the same material, sufficiently separated from each other to secure the

closure of the first door before the second can be opened.

In most Tropical residences, the number of doors is far in excess of

actual needs, it being nothing uncommon to find rooms with four or five

doors, all opening in the exterior. Though desirable and even necessary

for free ventilation, no room can possibly require more than a single

door opening on the outside, and in a well-planned house with suitable

corridors, there is no real necessity for more than one or two exterior

doors to the whole house. All outside doors, then, not absolutely

necessary as such, should be treated as windows and permanently closed

with single frames of wire gauze, so that the number of the more

expensive double spring doors may be reduced to a minimum. In Tropical

climates it is, however, essential that a considerable area of verandah

should be included within the protected area, as a good deal of time is

necessarily most pleasantly spent in the verandah, not only in the

evening, but during the rains throughout the whole day. On this account

a northern verandah should be the one selected for protection in this

way.

[Illustration: FIG. 11.--Railway servant’s cottage in the Roman

Campagna, protected against the entry of mosquitoes by Professor Celli’s

method.]

The main obstacle to the adoption of the plan is undoubtedly the

expense, which would amount to £20 or £30 for an ordinary Indian

bungalow, and though this may appear by no means prohibitory in the case

of permanent residents, it puts the matter practically out of the reach

of even well-paid officials, as they can never count on enjoying the

benefits of any permanent improvement of this sort for more than a few

months; the wisdom of our rulers almost always leading them to transfer

an officer to another station long before he is likely to have

thoroughly learned his way about the streets of the town he has to

govern.

[Illustration: FIG. 12.--Ground-plan of an existing up-country Indian

Bungalow, to show method of adapting one (Professor Celli’s plan) of

wire gauze protection. The dotted lines represent the wire gauze

screens. _D.G.D._, double spring doors of wire gauze; _S.G.D._ single

spring door of wire gauze combined with existing ordinary door; _B.R._,

bath-room; _D.R._ dressing-room. Scale, 18′ = 1″.]

On the preceding page is given the ground plan of an actually existing

“up-country” bungalow of a very usual type in which the spaces guarded

by gauze are indicated with dotted lines. The original doors are shown

as complete, and the windows as shaded gaps. As will be seen, the number

of doors for actual traffic is reduced to three, not counting those of

the bath-rooms, which, being but little used during the hours of

mosquito activity, have been left with single spring doors only.

There are many situations, such as houses necessarily placed in the

midst of canal irrigation--Government canal bungalows for example--in

which no other method of protection is in any way practicable, and it is

clearly the duty of Government to protect officers, such as irrigation

and forest officials, whose duties lead them into specially dangerous

places, in this way in all cases where official quarters are provided.

There cannot be the least doubt, too, that the capital so spent would be

found to be a highly remunerative investment, and that this would be

equally the case if steps were taken to protect all barracks in this way

instead of wasting the costly soldier by needless invaliding. In the

case however, of civil and military officers, who have to rent their

houses from landlords, who are generally needy natives, with neither

inclination, nor means, to provide costly improvements, the utmost they

can do is to provide themselves with a sufficiency of portable folding

gauze screens to protect their sleeping chambers. In any given locality

there is generally some approach to a standard size for doors and

windows, so that by the exercise of a little ingenuity it ought to be

possible to adapt a set of folding screens to any room, allowing them

when too large to overlap the sides of the embrasure, and supplementing

deficiencies with sacking or rough planking. In India, for example, door

openings are usually about 7 ft. by 4 ft., and screens opening out to

this size might be utilised in most houses. It is obvious that the set

of frames provided for each room must include one filled with a small

spring door. I believe that a number of screens capable of opening out

to something larger than the dimensions of an average doorway would be

less bulky than any possible portable mosquito-proof room--and at any

rate a complete set for an ordinary family would weigh far less than an

average piano, and would be far more conducive to health. It should be

added that in this, and in all cases where single rooms are placed under

protection, all doors, internal as well as external, must be protected,

and as they would in no way prevent the use of a punkah, they would be

an enormous improvement on the ordinary mosquito net, which, failing

such appliances, is an absolute essential to health during the malarious

season.

Where nothing more permanent is possible, recourse must be had to

mosquito nets, which can with care be made to afford a fairly thorough

protection during the most dangerous portion of the twenty-four hours.

It is a mistake, however, to trust to tucking the net in beneath the

mattress, as this is apt to become disarranged during the night, and it

is further very undesirable that the net should touch any portion of the

mattress at all, as if it does so, the net can be also touched by the

sleeper, who thus readily exposes himself to being bitten through the

net. The top of the frame of the net should, therefore, be made both

longer and wider than the bed and should be long enough to reach easily

to the floor, with which its edge should be kept in contact by means of

a hem weighted with sand or small shot.

I have seen, especially in Calcutta, several attempts at the

construction of curtains so large as to admit of a punkah being swung

inside them, the top of the curtains being carried right up to the

ceiling, and the strap of the punkah being pulled through a sort of

sleeve; but the arrangement is necessarily an expensive one, and the

swing of the punkah is always more or less crippled by the sleeve. A

better plan is, I think, to make the frame supporting the netting very

low, scarcely higher in fact than that of a child’s cot, so that the

punkah swinging outside, but almost in contact with it, still passes

within a foot or two of the sleeper. Such an arrangement is rather

awkward to get in and out of, but this drawback is a very trifling one,

compared with the enormous advantage of combining the protection of the

net with the comforts of a punkah. For this idea I am indebted to Mr.

Symmonds, of Rosa, whose contrivance I presume it is, as I have

certainly never seen beds fitted in this way in anyone else’s house. For

sleeping out of doors in the open, the net must, however, be of the

usual fashion; as if the wind be at all strong, a weighted hem would not

suffice to keep the net closed. It is therefore important when sleeping

out to use a large bed, so that contact with the net may be less likely

to happen; and the top of the net should be formed of ordinary calico,

so as to keep off the dew. Not unfrequently the mesh of the netting sold

for making mosquito nets is too coarse, a point of some importance, as

Anopheles mosquitoes in particular are adepts in creeping through small

openings; and as the writer has found it impossible to confine them in

enclosures formed of the coarser patterns of net, it may be concluded

that such a material is equally inadequate to keep them out.

[Illustration: FIG. 13.--Bed arranged with a low mosquito-net frame,

with punkah above it.]

References to the protection against malaria afforded by mosquito nets

by observant sportsmen and explorers are to be found in numbers of books

of travel and adventure published long before any explanation of the

fact was possible; and during the malarious season it is nothing better

than culpable rashness to pass the night without this protection, except

in a room properly guarded with wire netting. It is quite common to hear

it asserted that a punkah alone is sufficient protection, but this is an

entire mistake, as I have repeatedly watched a mosquito making a

comfortable feed on my person within a few inches of a spot actually

flicked by the towel which it is usual to pin on to the lower edge of

the punkah. In non-malarious months, such as the hot dry weather

preceding the rains in northern India, there is, of course, no need of a

net except as a matter of protection against the harmless, but very

annoying, Culices that are very common at that season of the year; and

in spite of its inferior protection against being bitten, many will

prefer the freer air current afforded by the punkah. After the

commencement of the rains, however, the fact cannot be too strongly

emphasised that to sleep without the protection of a net is to wilfully

expose oneself to a real and ever-present danger.

In the matter of preventing mosquitoes from becoming infected it is

obvious that comparatively little can be effected by the private

individual. All he can do is to bear in mind that persons suffering from

malaria are as great and real a danger to their neighbours as those

affected with scarlet fever, small-pox or any other communicable malady,

and accordingly to try to limit the number of such cases amongst his

servants and dependents. In the great majority of cases in all

probability, the mosquito that infects the European resident has been

infected by a case amongst his servants; and quite apart from

philanthropic considerations, it is most important to detect all such

cases and have them treated with quinine.

It is a well-known fact that, even where the drug appears to fail to

cure the disease, it is very difficult to find the malarial parasite in

the blood of cases that have been well dosed with the drug, and as there

must be parasites present in the blood itself in order to convey

infection to the mosquito, it is obvious that, apart from its curative

action, quinine may also be said to act as a disinfectant. On this

account, where the removal of a servant “down with fever” cannot be

arranged, it is highly important that he should be liberally dosed with

quinine; and it must be remembered that it is not sufficient to supply

him with the drug, but that it is also necessary to see it taken. In

some countries, the native is so truly a child in intellect, that he has

to be treated like one if a bitter drug is to be administered; while the

Indian, though in no way wanting in intelligence, has often a prejudice

against quinine owing to the active propaganda against the drug preached

by the Baids and Haqims, or practitioners of the indigenous systems of

medicine. As a matter of fact, I believe these men use quinine largely,

but they take care not to let their patients know they are taking a drug

which can be got for a halfpenny a full dose at any post office, and try

to prevent the spoiling of their market by promulgating all sorts of

fables as to its dangerous and harmful character.

According to the queer phraseology in vogue amongst these folks--and it

is not so long ago since it was employed also in Europe--fever is a cold

disease which by an attractive paradox should be treated by cold remedy,

while quinine is made to belong to the opposite category of medicinal

agents. It is as well, then, to be prepared for objections of this sort;

but, as a rule, the personal influence of an European employer will

suffice to secure the taking of the medicine, provided he will take the

trouble to personally see it swallowed.

Liable as all residents in the Tropics are to be attacked with fever at

times and places where skilled medical assistance is not obtainable, it

may be well to conclude this chapter with a few words on the treatment

of the malady. This really resolves itself into the adequate

administration of quinine; for provided a sufficiency of the drug can be

got into the circulation, it will, I believe, always cure malaria; but

it is one thing to make the sick man swallow the drug and another to

secure a sufficiency of it being absorbed into the blood; and unless

this takes place, the remedy can have no more effect than as much

oatmeal or any other inert substance. Anyone who has suffered from a

severe attack of malaria, or had the nursing of a case, must have

noticed that want of power to tolerate or digest even the lightest food,

is one of its most prominent symptoms. In the more virulent type of the

disease, nausea and vomiting is one of its most distressing features,

and are nothing more than the outward manifestations of the fact that

the digestive organs have ceased to perform their functions, and this

may be equally the case, even where these additional evidences of the

fact are not so prominent.

A little reflection will show that it is very unlikely that quinine or

any other drug will be absorbed by a stomach that can no longer deal

with even the lightest food, and hence it is not surprising that the

severer forms of remittent fever will often resist quinine for long

periods. For the same reason that quinine so often fails to do good in

virulent cases, it is equally obvious that it is unlikely to do harm,

and the absurd theory that “blackwater fever” is the outcome of treating

malaria with quinine may now, I think, be said to be abandoned by all,

save perhaps one or two of its original propounders; for though quinine

appears to be of but little value in the treatment of that doubtfully

malarial disease, it has now again and again been shown to occur in

patients who have taken no quinine at all.

It cannot, therefore, be too strongly insisted upon that, in spite of

failure to produce immediate effects, the administration of quinine

should be steadily persisted in, as sooner or later in almost all cases

a sufficiency will be absorbed to check the disease.

From what has been said, it is clearly important to do our best to put

the digestive organs, if possible, in a position to perform their

functions, and as in the majority of cases the sluggish bowels are

loaded with half-digested or undigested food, it is a good general rule,

as a preliminary to the administration of quinine, to administer some

unirritating laxative, for which purpose nothing can be better than our

old friend and bugbear of childhood, castor oil; and the dose should be

repeated whenever constipation becomes a symptom in the course of the

case. Once the laxative has acted, the sooner quinine is administered

the better, and, unless the patient be one of those unfortunately

constituted persons who are unable to take it--and there are some few to

whom quinine seems as poisonous as it is to the malarial parasite--it

should be given in full doses to the extent of 20 or even 30 grains (1

to 2 grammes of metric system) in the twenty-four hours. A dose of 10

grains, followed by others of 5 grains each, will usually be found a

convenient plan of administration; but there are cases which do better

with smaller doses more frequently administered. The best way to give it

is, I think, to stir up the powder in a little milk; and it may be well

here to offer a word of caution as to the employment of the drug in the

form of tabuloids. For some reason, the drug appears difficult of

digestion in this form, for I have repeatedly found fever yield at once

to the ordinary powdered form of the drug, after days of fruitless

treatment with quinine tabuloids obtained from firms of so high a

reputation that the suggestion of the substitution of some less

expensive material for quinine is quite untenable. The indiscriminate

use, too, of antipyrin, phenacetin, &c., is also to be deprecated. They

are all powerful depressants; and though they afford great relief to the

aches and weariness of an attack of fever, undoubtedly have no effect

whatever in curing the disease, even if they do not, as I have often

been inclined to suspect, tend to prolong it. Where the suffering is

very acute, an occasional dose may be of use for securing rest, but

anything like continuous dosing with medicines of this sort should be

carefully avoided. On the other hand, the old-fashioned “fever mixture,”

composed of ten or fifteen drops of nitrous ether with a drachm of

Minderus’ spirits (_liquor ammoniæ acetatis_), every four hours, in a

wineglass of water, is often of great use in favouring perspiration,

besides acting as a useful diuretic; and may be recommended as not only

affording much relief to the patient’s subjective symptoms, but also of

being absolutely safe even in inexperienced hands.

Except in the weakness of very prolonged attacks, stimulants should be

but sparingly given, but they should not be withheld when the patient is

flagging, and obviously falling into what is known as a “typhoid state.”

It is almost needless to remark that care is required in the matter of

diet. During the febrile periods “slops” only should be given, and then

in not too large quantities at a time; but in those cases where there is

a distinct fever-free interval between the paroxysms of the disease, a

great deal of license may be allowed, and solid food of a light

digestible sort is often not only well tolerated, but even beneficial,

while it is almost needless to say that these intervals of returned

digestive power should always be seized upon to get a liberal supply of

quinine into the system. During convalescence the administration of 10

to 15 grs. a day of quinine should be maintained for at least a week

after the disappearance of all febrile symptoms, and some ordinary

tonic, such as Easton’s syrup, is often useful in facilitating the

return to strength.

The least sign of a relapse, as evidenced by a rise of temperature, of

however temporary a character, should be met with a further treatment

with quinine for at least a week or ten days, as it is a clear sign that

the disease is scotched, but not killed, and that some of the parasites

are still lingering, in a latent condition, within the system; for the

patient cannot really be considered as cured till the last of these is

put an end to.

The length to which this chapter has attained may be justified by the

fact that the universality and the extent of the mischief wrought by

malaria in tropical climates renders the subject by far the most

important of all in connection with the preservation of health in the

tropics; and the writer trusts his readers may be moved to do as much as

they possibly may to preserve themselves and their neighbours from the

havoc wrought by this insidious disease, for without an informed and

intelligent public opinion to back them, no possible efforts on the part

of sanitary officials and medical men can be expected to exercise any

great or lasting effects on the prevalence of the disease.

Climate and Health in Hot Countries and the Outlines of Tropical Climatology A Popular Treatise on Personal Hygiene in the Hotter Parts of the World, and on the Climates That Will Be Met Within Them. · 第 7 / 11 章