MALARIA: THE PESTILENCE THAT WALKETH IN DARKNESS; THE GREATEST FOE OF THE PIONEER

Malaria has probably killed more human beings than all the wars that have ever devastated the globe. Some day the epic of medicine will be written, and will show what a large and unexpected part it has played in the progress of civilization. Valuable and essential to that progress as were the classic great discoveries of fire, ships, wheeled carriages, steam, gunpowder, and electricity, they are almost paralleled by the victories of sanitary science and medicine in the cure and prevention of that greatest disrupter of the social organism-disease. No sooner does the primitive human hive reach that degree of density which is the one indispensable condition of civilization, than it is apt to breed a pestilence which will decimate and even scatter it. Smallpox, cholera, and bubonic plague have blazed up at intervals in the centres of greatest congestion, to scourge and shatter the civilization that has bred them. No civilization could long make headway while it incurred the dangers from its own dirtiness; and to-day the most massive and imposing remains of past and gone empires are their aqueducts, their sewers, and their public baths. What chance has a community of building up a steady and efficient working force, or even an army large enough for adequate defense, when it has a constant death-rate of ten per cent per annum, and an ever recurrent one of twenty to thirty per cent, by the sweep of some pestilence? The bubonic plague alone is estimated to have slain thirty millions of people within two centuries in Mediaeval Europe, and to have turned whole provinces into little better than deserts.

In malaria, however, we have a disease enemy of somewhat different class and habits. While other great infections attack man usually where he is strongest and most numerous, malaria, on the contrary, lies in wait for him where he is weakest and most scattered, upon the frontiers of civilization and the borders of the wilderness. It is only of late years that we have begun to realize what a deadly and persistent enemy of the frontiersman and pioneer it is. We used to hear much of climate as an obstacle to civilization and barrier to settlement. Now, for climate we read “malaria.” Whether on the prairies or even the tundras of the North, or by the jungles and swamps of the Equator, the thing that killed was eight times out of ten the winged messenger of death with his burden of malaria-infection. The “chills and fever,” “fevernager,” “mylary,” that chattered the teeth and racked the joints of the pioneer, from Michigan to Mississippi, was one and the same plague with the deadly “jungle fever,” “African fever,” “black fever” of the tropics, from Panama to Singapore. Hardly a generation ago, along the advancing front of civilization in the Middle West, the whole life of the community was colored with a malarial tinge and the taste of quinine was as familiar as that of sugar. To this day, over something like three-quarters of the area of these United States, the South, Middle West, and Far West, if you feel headachy and bilious and “run down,” you sum it all up by saying that you are feeling “malarious.” Dwellers upon the rich bottom-lands expected to shake every spring and fall with almost the same regularity as they put on and shed their winter clothing. Readers of Frank Stockton will remember the gales of merriment excited by his quaint touch of the incongruous in making the prospective bridegroom of the immortal Pomona change the date of their wedding day from Tuesday to Monday, because, on figuring the matter out, he had discovered that Tuesday was his “chill-day.”

Though the sufferer from ague seldom received very much sympathy at the time, but was considered a fair butt for genial ridicule and chaff, yet even there the trouble had its serious side. Through all those communities there stalked a well-known and dreaded spectre, the so-called “congestive chill,” what is now known in technical language as the pernicious malarial paroxysm. These were like the three warnings of death in the old parable. You would probably survive the first and might never have another; but if you had your second, it was considered equivalent to a notice to quit the country promptly and without counting the cost. In my boyhood days in the Middle West, I can recall hearing old pioneers tell of little groups of one or more families moving out on to some particularly rich and virgin bottom-land and losing two or three or more members out of each family by congestive chills within the first year, and in some cases being driven in from the outpost and back to civilization by the fearful death-loss.

A pall of dread hangs over the whole west coast of Africa. The factories and trading-posts are haunted by the ghosts of former agents and explorers who have died there. Some years ago one German company had the sinister record that of its hundreds of agents sent out to the Gold Coast under a three years’ contract, not one had fulfilled the term! All had either died, or been invalided and returned home. It was malaria more than any other five influences combined that thwarted the French in their attempt to dig the Panama Canal and that made the Panama Railroad bear the ghastly stigma of having built its forty miles of track with a human body for every tie.

Malaria ever has been, and is yet, the great barrier against the invasion of the tropics by the white races; nor has its injurious influence been confined to the deaths that it causes, for these gaps in the fighting line might be filled by fresh levies drawn from the wholesome North. Its fearfully depressing and degenerating effects upon even those who recover from its attacks have been still more injurious. It has been held by careful students of tropical disease and conditions that no small part of that singular apathy and indifference which steal over the mind and body of the white colonist in the tropics, numbing even his moral sense, and alternating with furious outbursts of what the French have termed “tropical wrath,” characterized by unnatural cruelty and abnormal disregard for the rights of others, is the deadly work of malaria. It is the most powerful cause, not merely of the extinction of the white colonist in the tropics, but of the peculiar degeneracy-physical, mental, and moral-which is apt to steal over even the survivors who succeed in retaining a foothold. Two particularly ingenious investigators have even advanced the theory that the importation of malaria into the islands of Greece and the Italian peninsula by soldiers returning from African and Southern Asiatic conquests had much to do with accelerating, if not actually promoting, the classic decay of both of these superb civilizations.

To come nearer home, there can be little question that the baneful, persistent influence of malaria, together with the hookworm disease, has had much to do both with the degeneracy of the Southern “cracker,” or “mean white,” and with those wild outbursts of primitive ferocity in all classes which take the form of White Cap raids and lynching mobs.

However this may be, the disease and the colonization habit brought in a crude way their own remedy. The Spanish conquerors of Peru were told by the natives that a certain bark which grew upon the slopes of the Andes was a sovereign remedy for those terrible ague seizures. Indian remedies did not stand as high in popular esteem as they do now; but they were in desperate straits and jumped at the chance. To their delight, it proved a positive specific, and a Spanish lady of rank, the Countess Chincona, was so delighted with her own recovery that she carried back a package of the precious Peruvian bark on her return to Europe, and endeavored to introduce it. So furious was the opposition of the Church, however, to this “pagan” remedy that she was completely defeated in her praiseworthy attempt and was obliged to confine her ministrations to those who belonged to her, the peasantry on her own estate. About half a century later, the new remedy excited so much discussion by the numerous cures that it effected, that it was considered worthy of a special council of the Jesuits, who formally pronounced it suitable for the use of the faithful, thereby attaching to it for many years the name of “Jesuit’s bark.” Virtue, however, is sometimes rewarded in this world, and the devoted and enlightened countess has, all unknown to herself, attained immortality by attaching her name, Chincona, softened into cinchona, and hardened into quinine, to the greatest therapeutic gift of the gods to mankind. It is not too much to say that the modern colonization of the tropics and subtropics by Northern races, which is one of the greatest and most significant triumphs of our civilization, would have been almost impossible without it. Its advance depended upon two powders, one white and the other black,-quinine and gunpowder.

For nearly three centuries we rested content with the knowledge that in quinine we had a remedy for malaria, which, if administered at the proper time and in adequate doses, would break up and cure ninety per cent of all cases. Just how it did it we were utterly in the dark, and many were the speculations that were indulged in. It was not until 1880, that Laveran, a French army surgeon stationed in Algeria, announced the discovery in the blood of malarial patients of an organism which at first bore his name, the Hematozoon-Laveran, now known as the Plasmodium malariae. This organism, of all curious places, burrowed into and found a home in the little red corpuscles of the blood. At periods of forty-eight hours it ripened a crop of spores, and would burst out of the corpuscles, scattering throughout the blood and the tissues of the body, and producing the famous paroxysm. This accounted for the most curious and well-marked feature of the disease, namely, its intermittent character, chill and fever one day, and then a day of comparative health, followed by another chill day and so on, as long as the infection continued. One problem, however, was left open, and that was why certain forms of the disease had their chills every fourth day and so were called quartan ague. This was quickly solved by the discovery of another form of the organism, which ripened its spores in three days instead of two. So the whole curious rhythm of the disease was established by the rate of breeding or ripening of the spores of the organism. Later still another form was discovered, which had no such regular period of incubation and gave rise to the so-called irregular, or autumnal, malarial fevers. That form of the fever which had a paroxysm every day, the classic quotidian ague, remained a puzzle for a little longer, but was finally discovered to be due chiefly to the presence of two broods, or infections, of the organism, which ripened on alternate days and hence kept the entire time of the unfortunate patient occupied.

The mystery of the remedial effect of quinine was also solved, as it was found that, if administered at the time which centuries of experience has shown us to be the most effective, between or shortly before the paroxysms, it either prevented sporulation or killed the spores. So that at one triumphant stroke the mystery of centuries was cleared up.

But here will challenge some twentieth-century Gradgrind: “This is all very pretty from the point of view of abstract science, but what is the practical value of it? The discovery of the plasmodium and its peculiarities has merely shown us the how and the why of a fact that we had known well and utilized for centuries, namely, that quinine will cure malaria.” Just listen to what follows. The story of the plasmodium is one of the most beautiful illustrations of the fact that there is no such thing as useless or unpractical knowledge. The only thing that makes any knowledge unpractical is our more or less temporary ignorance of how to apply it. The first question which instantly raised itself was, “How did the plasmodium get into human blood?” The very sickle-shape of the plasmodium turned itself into an interrogation mark. The first clew that was given was the new and interesting one that this organism was a new departure in the germ line in that it was an animal, instead of a plant, like all the other hitherto known bacilli, bacteria, and other disease-germs.

It may be remarked in passing that its discovery had another incidental practical lesson of enormous value, and that was that it paved the way for the identification of a whole class of animal parasites causing infectious diseases, which already includes the organisms of Texas fever in cattle, dourine in horses, the tsetse fly disease, the dreaded sleeping sickness, and finally such world-renowned plagues as syphilis and perhaps smallpox.

Being an animal, the plasmodium naturally would not grow upon culture-media like the vegetable bacilli and bacteria, and this very fact had delayed its recognition, but raised at once the probability that it must be conveyed into the human body by some other animal. Obviously, the only animals that bite our human species with sufficient frequency and regularity to act as transmitters of such a common disease are those Ishmaelites of the animal world, the insects. As all the evidence pointed toward malaria being contracted in the open air, attested by its popular though unscientific name mal-aria, “bad air,” and as of all forms of “bad air” the night air was incomparably the worst, it must be some insect which flew and bit by night; which by Sherlock Holmes’s process promptly led the mosquito into the dock as the suspected criminal. It wasn’t long before he was, in the immortal language of Mr. Devery, “caught with the goods on”; and in 1895 Dr. Ronald Ross, of the Indian Medical Service, discovered and positively identified the plasmodium undergoing a cycle of its development in the body of the mosquito. He attempted to communicate the disease to birds and animals by allowing infected mosquitoes to bite them, but was unsuccessful. Two Italian investigators, Bignami and Grassi, saw that the problem was one for human experiment and that nothing less would solve it. Volunteers were called for and promptly offered themselves. Their blood was carefully examined to make sure that they were not suffering from any latent form of malaria. They then allowed themselves to be bitten by infected mosquitoes, and within periods varying from six to ten days, eight-tenths of them developed the disease. It may be some consolation to our national pride to know that although the organism was first identified in the mosquito by an Englishman and its transmission to human beings in its bite by Italians, the first definite and carefully worked-out statement of the relation of the mosquito to malaria was made by an American, King of Washington, in 1882; though it is only fair to say that suggestions of the possible connection between mosquitoes and malaria had, so to speak, been in the air and been made from scores of different sources, from the age of Augustus onward.

Another mystery was solved-and what a flood of light it did pour upon our speculations as to the how and wherefore of the catching of malaria! In some respects it curiously corroborated and increased our respect for popular beliefs and impressions. While “bad air” had nothing to do with causing the disease, except in so far as it was inhabited by songsters of the Anopheles genus, yet it was precisely the air of marshy places which was most likely to be “bad” in this sense. So that, while in one sense those local wiseacres, who would point out to you the pearly mists of evening as they rose over low-lying meadows and bottom-lands, and inform you that there before your very eyes was the “mylary just a-risin’ out of the ground,” were ludicrously mistaken, in another their practical conclusion was absolutely sound; for it is in just such air, at such levels above the surface of the water, that the Anopheles most delights to disport himself. Furthermore, while all raw or misty air is “bad,” the night air is infinitely more so than that of the day, because this is the time at which mosquitoes are chiefly abroad. In fact, there can be little doubt that this is part of the foundation for that rabid and unreasonable dread of the night air which we fresh-air crusaders find the bitterest and most tenacious foe we have to fight. We have literally discovered the Powers of Darkness in both visible and audible form, and they have wings and bite, just like the vampire.

It was also a widespread belief in malarial regions that the hours when you are most likely to “git mylary inter yer system” were those just before and just after sundown; and now entomologists inform us that these are precisely the hours at which the Anopheles mosquito, the only genus that carries malaria, flies abroad.

Of course, a number of popular causes, such as bad drainage, the drinking of water from shallow surface wells, damp subsoils under the houses, and especially that peculiarly widespread and firmly held article of belief that new settlements, where large areas of prairie sod were being freshly upturned by the plough, were peculiarly liable to the attack and spread of malaria, had to go by the board,-with this important reservation, however, that almost every one of these alleged causes either implied or was pretty safe to be associated with pools or swamps of stagnant water in the neighborhood, which would furnish breeding-spots for the mosquitoes.

The discovery explains at once a score of hitherto puzzling facts as to the distribution of malaria. Why, for instance, in all tropical or other malarious countries, those who slept in second and third story bedrooms were less likely to contract the disease, supposedly because “bad air didn’t rise to that height,” is clearly seen to be due to the fact that the mosquito seldom flies more than ten or twelve feet above the level of the ground or marsh in which he breeds, except when swept by prevailing winds. It also explained why in our Western and Southwestern states the inhabitants of the houses situated on the south bank of a river, though but a short distance back from the stream, would suffer very slightly from malaria, while those living upon the north bank, half a mile back, or even upon bluffs fifteen or twenty feet above the water level, were simply plagued with it. The prevailing winds during the summer are from the south and mosquitoes cannot fly a foot against the wind, but will fly hundreds of yards, and even the best part of a mile, with it. The well-known seasonal preference of the disease for warm spring and summer months, and its prompt subsidence after a killing frost, were seen simply to be due to the influence of the weather upon the flight of mosquitoes. Shakespeare’s favorite reference to “the sun of March that breedeth agues” has been placed upon a solid entomological basis by the discovery that, like his pious little brother insect, the bee, the one converted and church-going member of a large criminal family, the mosquito hies himself abroad on his affairs at the very first gleam of spring sunshine, and will even reappear upon a warm, sunny day in November or December. Perhaps even some of the popular prejudice against “unseasonable weather” in winter may be traceable to this fact.

Granted that mosquitoes do cause and are the only cause of malaria, what are you going to do about it? At first sight any campaign against malaria which involves the extermination of the mosquito would appear about as hopeless as Mrs. Partington’s attempt to sweep back the rising Atlantic tide with her broom. But a little further investigation showed that it is not only within the limits of possibility, but perfectly feasible, to exterminate malaria absolutely from the mosquito end. In the first place, it was quickly found that by a most merciful squeamishness on the part of the plasmodium, it could live only in the juices of one particular genus of mosquito, the Anopheles; and as nowhere, not even in the most benighted regions of Jersey, has this genus been found to form more than about four or five per cent of the total mosquito population, this cuts down our problem to one-twentieth of its apparent original dimensions at once. The ordinary mosquito of commerce (known as Culex) is any number of different kinds of a nuisance, but she does not carry malaria.

Here the trails of the extermination party fork, one of them taking the perfectly obvious but rather troublesome direction of protecting houses and particularly bedrooms with suitable screens and keeping the inhabitants safely behind them from about an hour before sundown on. By this simple method alone, parties of explorers, of campers, of railroad-builders going through swamps, of the laborers on our Panama Canal, have been enabled to live for weeks and months in the most malarious regions with perfect impunity, so long as these precautions were strictly observed. The first experiment of this sort was carried out by Bignami upon a group of laborers in the famous, or rather infamous, Roman Campagna, whose deadly malarial fevers have a classic reputation, and has achieved its latest triumphs in the superb success of Colonel Gorgas at Panama. While this procedure should never be neglected, it is obvious that it involves a good deal of irksome confinement and interferes with freedom of movement, and it will probably be carried out completely only under military or official discipline, or in tropical regions where the risks are so great that its observance is literally a matter of life or death.

The other division of malaria-hunters pursued the trail of the Anopheles to her lair. There they discovered facts which give us practically the whip-hand over malarial and other tropical fevers whenever we choose to exercise it. It had long been known that the breeding-place of mosquitoes was in water; that their eggs when deposited in water floated upon the surface like tiny boats, usually glued together into a raft; that they then turned into larvae, of which the well-known “wigglers” in the water-butt or the rain-barrel are familiar examples; and that they finally hatched into the complete insect and rose into the air.

Obviously, there were two points at which the destroyers might strike, the egg and the larvae. It was first found that, while the eggs required no air for their development, the larvae wiggled up to the surface and inhaled it through curious little tubes developed for this purpose, oddly enough from their tail-ends. If some kind of film could be spread over the surface of the water, through which the larvae could not obtain air, they would suffocate. The well-known property of oil in “scumming over” water was recalled, two or three stagnant pools were treated with it, and to the delight of the experimenters, not a single larva was able to develop under the circumstances. Here was insecticide number one. The cheapest of oils, crude petroleum, if applied to the pool or marsh in which mosquitoes breed, will almost completely exterminate them. Scores of regions and areas to-day, which were once almost uninhabitable on account of the plague of mosquitoes, are now nearly completely free from these pests by this simple means. An ounce to each fifteen square feet of water-surface is all that is required, though the oiling needs to be repeated carefully several times during the season.

But what of the eggs? They require no air, and it was found impossible to poison them without simply saturating the water with powerful poisons; but an unexpected ally was at our hand. It was early noted that mosquitoes would not breed freely in open rivers or in large ponds or lakes, but why this should be the case was a puzzle. One day an enthusiastic mosquito-student brought home a number of eggs of different species, which he had collected from the neighboring marshes, and put them into his laboratory aquarium for the sake of watching them develop and identifying their species. The next morning, when he went to look at them, they had totally disappeared. Thinking that perhaps the laboratory cat had taken them, and overlooking a most contented twinkle in the corner of the eyes of the minnows that inhabited the aquarium, he went out and collected another series. This time the minnows were ready for him, and before his astonished eyes promptly pounced on the raft of eggs and swallowed them whole. Here was the answer at once: mosquitoes would not develop freely where fish had free access; and this fact is our second most important weapon in the crusade for their extermination. If the pond be large enough, all that is necessary is simply to stock it with any of the local fish, minnows, killies, perch, dace, bass,-and presto! the mosquitoes practically disappear. If it be near some larger lake or river containing fish, then a channel connecting the two, to allow of its stocking, is all that is required.

On the Hackensack marshes to-day trenches are cut to let the water out of the tidal pools; while in low-lying areas, which cannot be thus drained, the central lowest spot is selected, a barrel is sunk at this spot, and four or five “killie” fish are placed in it. Trenches are cut converging into this barrel from the whole of the area to be drained, and behold, no more mosquitoes can breed in that area, and, in the language of the day, “get away with it.”

Finally, most consoling of all, it was discovered that, while the ordinary Culex mosquito can breed, going through all the stages from the egg to the complete insect, in about fourteen days, so that any puddle which will remain wet for that length of time, or even such exceedingly temporary collections of water as the rain caught in a tomato-can, in an old rubber boot, in broken crockery, etc., will serve her for a breeding-place, the Anopheles on the other hand takes nearly three months for the completion of her development. So that, while a region might be simply swarming with ordinary mosquitoes, it would frequently be found that the only places which fulfilled all the requirements for breeding-homes for the Anopheles, that is, isolation from running water or larger streams, absence of fish, and persistence for at least three months continuously, would not exceed five or six to the square mile. Drain, fill up, or kerosene these puddles,-for they are often little more than that,-and you put a stop to the malarial infection of that particular region. Incredible as it may seem, places in such a hotbed of fevers as the west coast of Africa, which have been thoroughly investigated, drained, and cleaned up by mosquito-brigades, have actually been freed from further attacks of fever by draining and filling not to exceed twenty or thirty of these breeding-pools.

In short, science is prepared to say to the community: “I have done my part in the problem of malaria. It is for you to do the rest.” There is literally no neighborhood in the temperate zone, and exceedingly few in the tropics, which cannot, by intelligent cooeperation and a moderate expense, be absolutely rid first of malaria, and second of all mosquito-pests. It is only a question of intelligence, cooeperation, and money. The range of flight of the ordinary mosquito is seldom over two or three hundred yards, save when blown by the wind, and more commonly not more than as many feet, and thorough investigation of the ground within the radius of a quarter of a mile of your house will practically disclose all the danger you have to apprehend from mosquitoes. It is a good thing to begin with your own back yard, including the water-butt, any puddles or open cesspools or cisterns, and any ornamental water gardens or lily-ponds. These latter should be stocked with fish or slightly oiled occasionally. If there be any accumulations of water, like rain-barrels or cisterns, which cannot be abolished, they should either be kept closely covered or well screened with mosquito netting.

It might be remarked incidentally in passing, that the only really dangerous sex in mosquitodom, as elsewhere, is the female. The male mosquito, if he were taxed with transmitting malaria, would have a chance to reecho Adam’s cowardly evasion in the Garden of Eden, “It was the woman that thou gavest me.” Both sexes of mosquitoes under ordinary conditions are vegetable feeders, living upon the juices of plants. But when the female has thrown upon her the tremendous task of ripening and preparing her eggs for deposition, she requires a meal of blood-which may be a comfort to our vegetarian friends, or it may not. Either she requires a meal of blood to nerve her up to her criminal deed, or, when she has some real work to do, she has to have some real food.

The mosquito-brigade have still another method of checking the spread of malaria, at first sight almost a whimsical one,-no less than screening the patient. The mosquito, of course, criminal as she is, does not hatch the parasites de novo in her own body, but simply sucks them up in a meal of blood from some previous victim. Hence by careful screening of every known case of malaria, mosquitoes are prevented from becoming infected and transmitting the disease. Instead of the screens protecting the victims from the mosquitoes, they protect the mosquitoes against the victim.

This explains why hunters, trappers, and Indians may range a region for years, without once suffering from malaria, while as soon as settlers begin to come in in considerable numbers, it becomes highly malarious. It had to be infected by the coming of a case of the disease.

The notorious prevalence of malaria on the frontier is due to the introduction of the plasmodium into a region swarming with mosquitoes, where there are few window-screens or two-story houses.

No known race has any real immunity against malaria. The negro and other colored races, it is true, are far less susceptible; but this we now know applies only to adults, as the studies of Koch in Africa showed that a large percentage of negro children had the plasmodium in their blood. No small percentage of them die of malaria, but those who recover acquire a certain degree of immunity. Possibly they may be able to acquire this immunity more easily and with less fatality than the white race, but this is the extent of their superiority in this regard. The negro races probably represent the survivors of primitive men, who were too unenterprising to get away from the tropics, and have had to adjust themselves as best they might.

The serious injury wrought in the body by malaria is a household word, and a matter of painfully familiar experience. Scarcely an organ in the body escapes damage, though this may not be discovered till long after the “fever-and-ague” has been recovered from.

As the parasite breeds in the red cells of the blood, naturally its first effect is to destroy huge numbers of these, producing the typical malarial anæmia, or bloodlessness. Instead of 5,000,000 to the cubic centimetre of blood the red cells may be reduced to 2,000,000 or even 1,500,000. The breaking down of these red cells throws their pigment or coloring-matter afloat in the blood; and soaking through all the tissues of the body, this turns a greenish-yellow and gives the well-known sallow skin and yellowish whites of the eyes of swamp-dwellers and “river-rats.”

The broken-down scraps of the red blood-cells, together with the toxins of the parasite, are carried to the liver and spleen to be burned up or purified in such quantities that both become congested and diseased, causing the familiar “biliousness,” so characteristic of malaria.

The spleen often becomes so enormously enlarged that it can be readily felt with the hand in the left side below the ribs, so that it is not only relied upon as a sign of malaria in doubtful cases, but has even received the popular name of the “ague-cake” in malarious districts.

So full is the blood of the parasites, that they may actually choke up the tiny blood-vessels and capillaries in various organs, so as to block the circulation and cause serious and even fatal congestións. Obstructions of this sort may occur in the brain, the liver, the coats of the stomach, or intestines, and the kidneys; and they are the chief cause of the deadly “congestive chills,” or pernicious malarial paroxysms, which we have alluded to.

The kidneys are particularly liable to be attacked in this way; indeed, one of their involvements is so serious and fatal in the tropics as to have been given a separate name, “Blackwater fever,” from the quantities of broken-down blood which appear in and blacken the urine.

The vast majority of attacks of malaria are completely recovered from, like any other infection, but it can easily be seen what an injurious effect upon the system may be produced by successive attacks, keeping the entire body saturated with the poison; while there is serious risk of the parasite sooner or later finding some weak spot in the body,-kidney, liver, nervous system,-where its incessant battering works permanent damage.

How long the infection may lurk in the body is uncertain; certainly for months, and possibly for years. Many cases are on record which had typical chills and fever, with abundance of plasmodia in the blood, years after leaving the tropics or other malarious districts; but there is often the possibility of a recent re-infection.

Altogether, malaria is a remarkably bad citizen in any community, and its stamping-out is well worth all it costs.