Fig. 36.— Collections of water in the surface drains of an Indian cantonment. In the two upper photographs the pools are the result of an engineering expedient to break the fall of the water ; in the two lower they are accidental.
CONDITIONS INFLUENCING PREVALENCE 201 When travelling by rail during the rains in India, nothing is more common than to see all the country on one side flooded, while the other is comparatively dry. On this account railvs^ays, like canals, should, as far as possible, be made to follow the water-shed, and where this is out of the question, the provision of drainage openings should be much more liberal than is usually the case. It must be admitted that the European cannot be held entirely blameless in such matters. Putting aside the relationship of puddles to malaria, the presence of such irregular collections of water has long been recognised as unhealthy, and to say the very least they are untidy, and would not be tolerated in any advanced European country on this last score, if on no other. In countries such as India, our public works should be made standing objectlessons of the superiority of European methods and system. To remedy the results of past carelessness would undoubtedly be extremely costly ; but, in the majority of cases, they might have been entirely avoided by the exercise of a little care and foresight, and that with little or no enhancement of the first cost of the work. The mere fact that the excavation of a continuous ditch, in place of a chain of borrow pits, may endanger a railway embankment by "scouring," shows what efficient drainage cuts they might be made, and further conclusively demonstrates how badly they must be needed. Engineers, moreover, admit that for one embankment that succumbs to " scouring," a score collapse from the mere water-logging of their foundations in time of flood, so that the neglect to favour efficient drainage in every possible way can hardly be defensible, even from a strictly technical point of view ; and I cannot doubt that the ingenuity of our engineers is fully equal to devising a remedy for the scouring of drainage cuts placed beside embankments, if their provision be once admitted as a necessity. In the case of buildings again, in nine cases out of ten, the earth required for their plinths might be advantageously excavated so as to make drainage cuts to the nearest natural line of outfall and so become a source of improvement, instead of damage, but in practice the matter
20*2 GNATS OR MOSQUITOES — CHAPTER VIII is mostly left to the native contractor who takes up the job, and all he has to consider is how he may place the required number of cubic feet of soil in the place indicated, with the least possible expenditure of money or thought. The extent to which this burrowing for building material has been carried, in and about many Indian towns, is incredible, and the haphazard way in which it has been permitted to be carried on has resulted in the absolute wasting of large areas of valuable, culturable land, in a country where it can ill be spared. As a general rule, these "tanks" are far too dirty to favour malaria, for it is not uncommon to find that some zealous amateur sanitarian has deliberately carried the foul bazaar drainage into them ; but there are exceptions to this, and there can be no doubt that the taking of earth for building and domestic purposes should be systematised by local bye-law in every Indian municipal area ; for there are other tropical diseases than malaria, and the foul emanations of these lakes of putridity cannot fail to be harmful, even where they do not form nurseries for the transporters of malaria. The main obstacle to the removal of these tanks lies in the difficulty of obtaining, within any reasonable distance, sufficient soil to fill them in ; but it is not really necessary to fill them up to the level of the ground around them ; for, provided that all surface drainage into it be diverted, any given area is quite capable of absorbing all the rain that actually falls within its own limits, and provided it be carefully levelled, no permanent puddles will result, however low-lying it may be, at any rate in Upper India. Now, without exception, these hollows are very irregular, not only in outline, but in depth, and it is only their deepest parts that remain full for any considerable length of time, so that the only practicable way of dealing with them is not to attempt to fill them up, but to level the area they include ; obtaining the earth required to fill in the deepest parts by cutting away from the sides so as to bring them to a regular outline, and slope of bank.
A good deal of spoil too can usually be obtained by digging cuttings to cut off the drainage of the neighbouring
CONDITIONS INFLUENCING PREVALENCE 203 land, and in a few cases much more can be got by cutting a ditch from the new level of the floor of the old tank site to the nearest nullaJi.
The following photograph shows the progress of an experiment that I made in this direction. At the time of my taking over charge of the local jail, the site of the newly levelled ground in the foreground was occupied by a tank of some size, which had originated in the usual way ; in this case to get earth for the building of the jail. Being within Fig. 37. — Levelling up the site of aa actual Anopheles tank. jail limits, although in a waste corner, the contents were quite clean enough for the local Mosquito larva, and the place formed one of the principal breeding places supplying the jail. Some of the deepest parts must have been eight or ten feet below the level at which the prisoners are seen dumping the spoil gained from the banks ; and, one way and another, I got about a couple feet more of material, with the result that a plot of valuable garden land was substi-
204 GNATS OR MOSQUITOES — CHAPTER VIII tuted for an injurious collection of water. Moreover, as far as I can judge, the rental of such a plot would have paid well for the amount of labour expended. I was led to try the experiment by noticing a large levelled depression, which had once been an old-standing brick field, and which an enterprising native had converted into profitable garden ground, and finding that, though without any proper outfall, the owner was in no way troubled with flooding. In many cases in towns, hollows of this sort are grouped together in considerable numbers, with intervening strips of high ground, and, in such cases, these would supply ample material for levelling, and the results could scarcely fail to be remunerative, as cultivable land in such situations always commands a high rental.
The effects of the surroundings that go to make up the conditions of town as contrasted with country life are all in favour of the urban resident. Where indeed could a generation of Anopheles find a secure nursery for their larval youth in the heart of such cities as London or Paris ? Nearly forty years ago Dr. Wood, of Philadelphia, pointed out "the extraordinary and very important fact," that " miasmata are neutralised, decomposed, or in some other way rendered innocuous by the air of large cities. Though malarious diseases may rage round a city, and even penetrate the outskirts, yet they are unable to penetrate into the interior ; and individuals who never leave the thickly populated parts almost always escape " (" Chambers Encylop.," vi., p. 438, 1868). The true reason for this is, of course, the careful utilisation of every square foot of surface ; the grading and paving of the streets, and the resulting impossibility of the existence of puddles sufficiently permanent to rear a brood of larvae ; and it follows from this that it is only in towns in which the resources of pvilisation are highly developed that this favourable influence of urban life is very noticeable.
An unpaved, ill-drained town may be as malarious as any country district, and as a matter of fact, few of our Indian cities are sufficiently advanced in these respects to gain any marked advantage over the surrounding country.
CONDITIONS INFLUENCING PREVALENCE 205 Most of them have arisen from the growth and amalgamation of a number of contiguous villages, and strips and islands of the old rural area are commonly left between the more closely packed houses of the old village sites. The only " up country " city, indeed, with which I am personally acquainted which at all approximates to the conditions of our large European towns is Benares, but even there the back streets and lanes are mostly unpaved, and I have found puddles teeming with Anopheles larvae in the very heart of the sacred city, though most of these were fed from the municipal hydrants, the untoward effects of which have already been noticed in connection with the effects of water supply on malaria.
Fortunate indeed it is that such is the case, as, malaria or no malaria, the value of thase breathing spaces is incalculable, for a continuous mass of houses such as form our large European towns, inhabited by a population of oriental habits, would be a perfect hot-bed for the breeding of plague and other bacterial infections.
Outside the bazaars, or business quarters, continuous lines of houses are rare. In residential neighbourhoods, owing to the necessity for privacy imposed by their social system, each house is a hollow square of which one or more sides are usually simple walls of no great height. As not only the human inmates, but commonly also cattle and horses, have to be accommodated, the size of this inner court even in modest households is often considerable, and the residences of well-to-do citizens have often considerable gardens. The latter form ideal breeding places for mosquitoes of all sorts, but the domestic puddles of the more usual enclosures are generally far too foul for the larvae of even the none too fastidious An. Rossii, though C. fatigans breeds in abundance about them.
The anti-malarial influence, then, of town life is less marked in India than in Europe, but it is nevertheless, I am inclined to think, quite perceptible, for though no reliable statistics are available, most officers who have been engaged in our civil medical administration appear to have a general impression that their towns are less feverish than the districts surrounding them.
206 GNATS OR MOSQUITOES — CHAPTER VIII Judging from descriptions, this effect should be more marked in Chinese cities than in other types of oriental civilisation ; but whatever it may amount to, the advantage must be purchased at too high a price. When, however, the Indian townsman is driven to overcrowding by special local conditions, he packs with a closeness that puts the Western slum-dweller to shame, and an enormous population may be concentrated in an area too small to be beyond the influence of the nearest breeding places even in its most central parts.
There are, for example, parts of Bombay where the density of population probably exceeds that of the worst European slums, but the dimensions of this " congested area " are not considerable.
As, however, the domestic interiors are usually too unsavoury to furnish nurseries for the really dangerous species, it is certain that the paving and draining of our large towns will do much to diminish municipal malaria. A good deal indeed has been done, and is in progress in this direction, but as the constantly recurring phrase of conventional Indian self-depreciation has it, " We are very poor folk," and improvements that appear the simplest necessities of urban sanitation to the European expert are quite beyond the pockets of the community, however enlightened the views of the Government may be. The paving of streets and the introduction of systematic surface drainage are of course large and costly undertakings, which can only be carried out gradually, but it must not be supposed that nothing can be done in the mean time. Nine-tenths of the nurseries of Anopheles larvse that I have met with within municipal limits are of such small dimensions that they might be put an end to by means of a few shovels-full of earth, and a few men trained to systematically fill up the puddles as they formed might undoubtedly do a good deal to diminish municipal malaria. Such a measure is of course rather of the category to which belongs chemical disinfection, than to that of radical prevention, for I am perfectly aware that new puddles would form as fast as the old ones were filled up, but these could do no harm if filled up in their turn.
CONDITIONS INFLUENCING PREVALENCE 207 Let it be at once admitted that the extermination of Mosquitoes may be impracticable ; but it does not follow that we should fold our hands and make no effort to prevent their fullest multiplication. Every Anopheles puddle filled up means one focus the less of infectible material, and the mere fact that without any specially directed sanitary efforts the city of Rome is malaria free, though standing in the midst of most deadly surroundings, shows how much may be effected.
There are millions of unvaccinated persons in India, and everyone of them is a possible focus of variolous infection,, but no one can doubt that vaccination has effected an enormous diminution of small-pox in the country, though the impossibility of securing universal vaccination might have served equally well as an argument for attempting nothing in the matter. In the wide expanse of the country in general such detailed measures are certainly impracticable, but in limited areas, such as those of municipalities, much might undoubtedly be done by the intelligent application of our present knowledge, albeit of a " hand-to-mouth " character, and that at but a trifling cost. Much also might be done by the enforcement by municipalities of bye-laws prohibiting the indiscnminate honeycombing of the surface for earth for building and plastering purposes. Such a regulation need not give rise to any real inconvenience, as tanks and other excavations of a size unhkely to serve as nurseries for larvae are so numerous in most such municipal areas that it would cause no hardship to insist on the earth required for such purposes being taken from their banks. The systematic filling up of small depressions with any hard rubbish that may be available is another measure that obviously suggests itself, and as the most dangerous collections are generally quite small and shallow, need not be beyond the pecuniary resources of even small places.
In the North-west Provinces and Punjab I have rarely met with any large collection of water or "tank" within the limits of a native town which contained Anopheles larvae. Most of them, indeed, are too foul for even the least