224 GNATS OR MOSQUITOES — CHAPTER VIII exception of paraffin, and an aniline product called " larvicide," prepared by Weiler-ter-Meer, of Uerdingen, none are sufficiently powerful, in proportion to their cost, to be of any use on a practical scale. To these may be added tar, but the reports I have received as to the efficacy of this latter are so contradictory that there can be no doubt that it is very uncertain in its action, and it is hardly cheaper than paraffin, as to the efficiency of which, when properly applied there can be no doubt. Paraffin, it must be remembered, kills the larvoB, not by acting as a poison, but by choking them, the thin film which it forms on the surface preventing their getting access to the air ; and therefore to use it with success, care must be taken that it is made to spread over the entire surface. No very large quantity is required, but it is better to err on the side of liberality ; and according to my experience, the best and easiest way is to sprinkle it over the surface by one or two rapid sweeps from a fine-rosed watering pot. So employed, I have never known it fail, the larvse being all found dead in the course of a few hours.
" Larvicide " on the other hand acts as a poison, killing all larvEe within twenty-four hours, in a strength of about one in 7,000. The consignment I sent for had not come to hand when I left India, so that I know nothing of its powers from personal experiment ; but Celli appears to regard it as the only agent of the poisonous class that is cheap enough for use out of the laboratory. He appears to consider it as the most promising agent we have as yet at our disposal, and states that the cost of disinfection per cubic metre of water varies from lire 0'0056 to 0'0012, which is equivalent to saying that a shillingswoxth is sufficient for from 7,350 to 34,300 cubic feet of water. It is said to be not in the least injurious to plants, and that the water containing it may be drunk with impunity by men and cattle, but nevertheless to be lethal to most insects which are injurious to crops, so that it is particularly suitable for the treatment of such portions of rice swamps as are dangerously near habitations.
It has the further advantage over paraffin in the fact
CONDITIONS INFLUENCING PREVALENCE 225 that, not being volatile, its action is much more permanent, lasting for as long as two months, and there can be no doubt that it should be at least given a thorough trial. Assuming it to stand the test of practical work in the open, the question whether this or kerosine will be the cheaper agent to employ will depend on the depth of the water to be dealt with, as the entire bulk of the water must be rendered lethal ; whereas with kerosine depth need not be considered, and superficies is all that need be taken count of; so that where the water is shallow in proportion to its surface, paraffin will certainly be the cheaper ; while deep pools will be more economically dealt with by the new agent, the more so as the chemical would probably remain unaltered in the surface mud when it dried up, and more or less of it would be still available when redissolved on the reformation of the pool after fresh rain. It may be freely admitted taht in many places larvaebearing pools are so omnipresent that it may be practically impossible to deal with them in this, or any other detailed fashion, but it is equally true that many limited areas might be dealt with at but httle cost or trouble ; and it is to be hoped that some of our Colonial Governments may see their way to giving a fair trial to the methods above indicated in some selected localities.
Such being the state of our knowledge as to the sanitation of malaria on a large scale, it remains to be seen what can be done in the way of personal hygiene ; and here I believe it may be confidently asserted that much may be accomplished, though not of course absolutely without trouble, expense or other effort on the part of those who wish to protect themselves against this disease. Putting aside the prophylactic use of drugs, which may be better left to purely medical treatises, personal hygiene resolves itself into two classes of precautions, viz., by as far as possible preventing Mosquitoes from breeding in the nnmediate neighbourhood of our houses, and secondly, as private efforts of the first category can be only partially successful, to endeavour to avoid being bitten. Precautions of the first class have already been sufH- 15
226 GNATS OR MOSQUITOES — CHAPTER VIII ciently noticed, as they are merely such as have been suggested as corporate operations, but on a smaller scale ; but as the tropical resident usually lives in houses surrounded by a considerable area under his own control, a good deal more might be affected in this way than is usually the case in Europe. By a very little personal trouble and superintendence there should be no difficulty whatever in doing away with all breeding places within one's own compound, and an occasional round, followed by a coolie armed with a can of kerosine, would do much to keep them down in our immediate neighbourhood, while occasional fumigation with sulphur, especially of one's servants' houses, during the hybernating season would help to minimise the number of immigrants from the quarters of less careful folks. But our main reliance must be placed on precautions against being bitten, the principal of these being to endeavour to keep Mosquitoes out of our houses ; and the wonderful success obtained by Professor A. Celli in the case of certam railway employes on the line from Rome to Solmona shows that this is by no means as difficult as one would have expected.
No one can read his recent pamphlet " Sulla nuova profilassi della malaria," in which he gives an account of these results, without being convinced of this ; unless they prefer to regard the account as an effort of the imagination, a supposition which no one who has had the pleasure of talking with that distinguished hygienist would for a moment countenance. Selecting a notoriously malarious portion of the line, he had about half the cottages in which the railway men with their families live made roughly Mosquito-proof by protecting all the windows with fixed screens of wire gauze, and by providing all entrances with double spring doors of the same material, as shown in the accompanying illustration, reproduced by Professor Celli's courteous permission, while the other moiety were left in their original condition. The experiments have been now in progress for nearly three years, and counting each year as a separate observation, the results may be epitomised roughly as follows : In 25 protected cottages with a popu-
CONDITIONS INFLUENCING PREVALENCE 227 lation of 173 persons, only 8 were attacked with fever; whereas in 30 unprotected, having a population of 220, only 17 escaped the disease.
In several instances the compared cottages are the same building, unprotected in one year and protected in the following, and it must be admitted that a much smaller degree of success would warrant any reasonable person in giving the plan a thorough trial. All the same, I know well that what is comparatively easy in a small Italian cottage will be by no means so easy in our rambling Indian bungalows, with several doors to every room, and none of the joinery made to fit with any approach to accuracy. House Fig. 37a. — Railway servant's cottage in the Roman Campagna, protected against the entry of Mosquitoes by Professor Celli's method. building is as excellent in Italy as it is bad in India, and the careless finishing of most of our bungalows, especially of the roofs, would make it extremely dii^Hcult to keep out so importunate an intruder as the Indian Anopheles without extensive structural alterations. Then, too, I can easily picture how systematically Gunga Din and Nabbi Baksh would " forget " and carefully prop open the spring doors to save the trouble of shouldering them open ; but that might be got over by a little drilhng. In the type of bungalow
228 GNATS OR MOSQUITOES — CHAPTER VIII common in the Punjab, especially those which are what we speak of as " pacca " built, there w^ould be no great difficulty, but in the ordinary thatched houses of the North - West and lower India, it would tax the best ingenuity, and is practically impossible, unless we can substitute somethingbetter for the abominable "ceiling-cloth."
These vile dirt and vermin traps are, however, I am glad to say, rapidly disappearing. For the Burmese bungalow, it is difficult to suggest any plan of applying the method short of reconstruction.
I found that the cost of protecting the last bungalow I occupied would be, at present prices in India, about 300 rupees (i?20), but Celli tells me that suitable wire gauze (about 12 strands to the inch) of American manufacture is obtainable in Italy at much cheaper rates than we have to pay in India, and probably the price would lessen if there were a sufficient demand. Presuming the house to be adaptable, I believe the simplest plan will be to completely enclose the verandahs with gauze, providing each with a single set of doors. All the other openings would of course require fixed gauze frames, and doors opening elsewhere than on the verandahs would require to be separately fitted up. Possibly the bath-room doors might be left unaltered, their use being prohibited between dawn and 8 a.m., but it would certainly be preferable to fit them up also. The first cost would be of course considerable, but a considerable annual expenditure for " chiks " would be done away with. In this, however, as in the case of every essential of health and comfort, the main obstacle as far as officials are concerned, is that we are so constantly moved about from one station to another, that any attempts at improvements of a permanent character are ruinous, as the houses are rented from native landlords, who often are with difficulty persuaded to keep the roof over our heads weather-tight. In the case of permanent residents, however, I believe in the long run a distinct saving would result. " Chiks " are at the best a lame defence against either flies or mosquitoes, but if nothing better be obtainable must be made the best of, and this means that we must absolutely reverse our
CONDITIONS INFLUENCING PREVALENCE 229 present customs as to the times of openino; and closing them, as we now plan these so as to keep out, not mosquitoes, but flies, the habits of which are the very antithesis of those of mosquitoes.
At present they are kept more or less carefully closed during the day, and are rolled up at night. From an hour or two after sunrise till sunset, it little matters as regards Mosquitoes what is done with them, as the insects settle themselves down for their day's rest as soon as the sun is well up, and will not leave the shelter they have chosen unless they are obliged ; but at night every aperture must be carefully guarded and especially the period from 4 to 6 a.m. In the early evening dusk it is better to have everything opened, as just then Mosquitoes, if they can, leave the house to obtain vegetable food, but for all the rest of the darkness and dusk the more thoroughly a house can be kept Mosquito-proof the better.
It will be a long time, however, before Mosquito-proof houses become at all common in India, and for the present most of us will have to be content with Mosquito curtains. A compromise between the two would, however, be well within most people's resources, and far better than the stuffy old nets, which, in spite of my firm conviction of their necessity, are well nigh intolerable during " a break in the rains." For this reason no plan will ever be generally adopted in India which cannot be combined with the use of the punkah, and with the old-fashioned forms of the latter this is most difficult, though the handy little electric fans can be worked in almost any position. Unfortunately, power of this sort can be obtained in very few places, but it might be possible to employ the punkah coolies in working a small dynamo instead of pulling the rope ; though the difiiculty of getting any small defect remedied would still remain in all but the largest stations. A settled resident would find it simplest to make his sleeping apartment insect proof, but the vagabond ofdcial requires some contrivance that he can carry about with him with his other furniture when " transferred." For this I would suggest a portable miniature room formed of light wooden frames filled with
230 GNATS OR MOSQUITOES — CHAPTER VIII wire gauze, and hinged together into panels of convenient size, two of which should, however, be filled with thin planking, so as to protect the rest when packed up for transport. About 8 ft. square would be a convenient size, as to plan, but. to carry a punkah, the panels would have to be at least 10 ft. high, and even then the bed must be made as low as possible. Some contrivance to prevent it being shifted by the pull of the punkah would of course be required, and probably the best plan would be to secure the solid panels to the wall through which it is usually pulled ; but details may best be left to individual ingenuity. Whether the room be temporary or permanent, however, it is absolutely essential that all furniture and hangings should be absolutely excluded, excepting the beds, chair and small table, so that I fear the plan will hardly meet the aesthetic tastes of the " Memsahib."
"When " in camp," or on other temporary absences, we must still be content with the old curtains, and there is a right and a wrong way of hanging these, the latter of which is almost universally adopted, because it looks neater to spread them over the iron or wooden frame, and thereby leave gaps at the corners, which cannot be securely tucked in on account of the poles, than to suspend them inside the latter, so that these cannot obstruct complete security. The weak point of the curtains, however, is that unless the bed be very large and one can contrive to keep in the middle of it, one is sure to be bitten through them, owing to the limbs coming in contact with the net.
Many people have an idea that the punkah is an efficient protection against Mosquitoes, but this is entirely erroneous, and I have watched one filling herself, quite undisturbed by the towel pinned to the punkah-frill, which flicked my knee within a couple of inches of the spot she had selected, at every swing ; but those who blame us for sacrificing security to the comfort of a long-roped punkah, or for not swathing our limbs in thick woollen putties with the thermometer at 98"" in the shade, can know nothing of the climatic conditions under which we must contrive to exist, and forget that a restless night is a bad preparation for a tropical day, and
CONDITIONS INFLUENCING PREVALENCE 231 that most of us have other concerns to attend to, so that it is unreasonable to expect us to devote our lives to the prophylaxis of a single tropical disease ; though this is no argument against the adoption of such reasonable precautions as may be practicable. In the " hot weather" of the Punjab and North- West, though Culices, owing to our own carelessness, are usually in swarms, Anopheletes are so scarce that there is no real need of special precautions ; but as soon as the rains break curtains are indispensable to safety. This brings me to the question of clothing, which may be made to afford considerable protection without being otherwise unsuitable to the climate. I do not think our Indian species of Anopheles ever bite during the day, and the same seems to be true for West Africa, so that practically it is only during the evening that there is much chance of being bitten while awake, and not even then while moving about. The really dangerous time is during and after dinner, and the favourite point of attack the ankles, which are bitten through the thin socks that are usually worn. Unfortunately of late years, the sensible and cleanly custom of dressing for dinner in white drill jacket and pants is yielding to an absurd desire to assimilate our customs to those of Europe ; though how men of refined habits can reconcile themselves to wearing a garment which is nightly saturated with perspiration till it is worn out, passes my comprehension, and those who will sacrifice so, much are hardly likely to adopt trowser-straps, which would not be correct "form " in the black habiliments whereby the Indian Memsahib loves to keep green the ideals of the old country, though they formed a customary adjunct of the supplanted white costume, and would, applied to either, afford complete protection.
It is dangerous for a mere man to venture on the subject of ladies' dress, and in any case absolutely bootless ; but as fashion ordains that their evening costumes must sweep the ground, they can obviously protect themselves without straps, if they happen to think of it, and care to deny us the pleasure of glancing at the neat contour of a pointed shoe with an impossible heel; but the " low neck,"