HISTORY OF THE DISEASE IN MISSISSIPPI AND LOUISIANA.

It is significant that reliable evidence exists that anthrax prevailed in several localities of the lower Mississippi Valley at an early period, and has appeared locally at irregular intervals ever since. In 1836 a disease then known as "choking quinsy" prevailed in several counties of the swamp region of the State of Mississippi. The symptoms as described indicate that the disease was none other than true anthrax. In 1865 many cases were again reported from the same region, and in the spring of 1867, a season that was marked by an unusually severe drouth, an epidemic of anthrax set in, from which it is said that scarcely a mule escaped and 90 per cent of those affected died; years elapsed before the planters recovered from their losses. Since 1867 the disease has prevailed more or less in the same localities, and the years 1875, 1876, 1881, 1882, and 1889 were marked by light epidemics. In the northern part of the neighboring State of Louisiana the disease seems likewise to have prevailed for a considerable period, and in the scant literature upon the subject occasional reference is made to local outbreaks of anthrax there, or of a strikingly similar disease, for a period covering almost half a century. In the same parishes that were affected in Louisiana in 1896 an epidemic, far less fatal and more restricted in area, occurred in 1884; but since then this section is said to have been practically free from the disease.

PROBABLE ORIGIN OF THE DISEASE.

The exact origin of this epidemic is not known, but with the scientific knowledge that is now had of the cause of anthrax, and of the meteorological and other conditions that favor its development and spread, the probable origin can be surmised with considerable confidence.

Anthrax is said to have been occasionally observed in a sporadie form in the alluvial districts of southern Louisiana ever since the settlement of that country. Authentic records of its ravages, however, are somewhat scarce, and up to recent years a lack of scientific knowledge of the pathology of the disease has made intelligent investigation impossible. It is now, however, a well-known characteristic. of this malady that when it is once introduced upon premises the soil, grass, plants, water, and other substances are liable to become impregnated with the germs of the disease. These germs are then very retentive of vitality and may remain pathogenic for years, so that animals which afterwards graze upon these lands or are fed upon the products of them are liable to contract the contagion. From the most remote times, in all countries where anthrax has prevailed, lands upon which it has existed have been observed to be diseaseproducing agents for long periods afterwards, though the cause was unknown.

Existing facts indicate that anthrax is enzootic in certain localities of Mississippi and Louisiana and that the present outbreak probably has some unknown correlation with outbreaks of the past. Indications point suggestively to the fact that certain localities of these States may be impregnated with the germs of the disease; and it is important to observe that the climate and soil of the low-lying lands of the Mississippi Valley are of that character which is known to be propitious to the long conservation of anthrax germs, and that meteorological conditions often prevail there which are extremely favorable to their dissemination from one locality to another.

The localities infected in 1896 lie in the rich and fertile alluvial bottoms of the Mississippi Valley, and border either upon the Mississippi River or its tributes. The infected lands are invariably low, usually lying between the rivers and the adjacent uplands, and are interspersed with many swamps. These lands are almost yearly enriched in organic matter by springtime inundations. After the subsidence of the floods the favoring influence of a warm climate induces a rank and luxuriant growth of vegetation, but all extensive depressions in the soil are left covered with stagnant pools and the water stands deep in the ponds and marshes. Occasionally, as was the case in the summer of 1896, drouths of long duration follow; the ponds left by the inundations then subside; the herbage becomes withered; the pools, marshes, and smaller streams fall to a low level or dry up entirely; herbivorous animals are then compelled to seek water in the low-lying swamps and to graze either upon the rough forage of dried up and dusty pastures or upon the greener vegetation of low lands from which the water subsides only in seasons of drouth.

In all anthrax-infected countries it has been observed for centuries that a mysterious correlation existed between such conditions as the above-that is, with respect to soil, temperature, humidity, inundations, and drouths-and outbreaks of this peculiarly fatal disease. This correlation was long erroneously regarded as being that of cause and effect, but in recent years the science of bacteriology has demonstrated that these natural conditions simply furnish favorable media for the preservation of the germs and for the development of the disease and are in no way its direct cause.

THE CAUSE OF ANTHRAX.

Nothing is more certain in medical or veterinary science than that the cause of anthrax, and the only cause, is the invasion of the blood of animals by a minute parasitical plant, the Bacillus anthracis, or by its more minute seeds, called spores, both invisible except under a powerful microscope. Where and how these vegetable organisms originated can probably never be known, for the disease which they or their seeds alone can cause has existed in many widely separated countries from remote antiquity. It is only certain that their exist

ence in nature was first discovered in the animal system by Davaine, who in 1850 demonstrated their presence in the blood of animals affected with anthrax, though he had no suspicion then that the plant caused the disease. The history of this microorganism therefore dates from its discovery in the animal system. Its presence elsewhere in nature-in water, upon vegetation, or in soil-whether in the form of plant or seed, is always regarded as being traceable to some former connection with animal life.

The vitality of the Bacillus anthracis depends upon two conditions, a temperature of not less than 70° F. and the presence of oxygen. In its natural habitat-the blood of warm-blooded, living animalsthese two requisites to its life are furnished by natural heat and respiration. Under these conditions these parasitical plants pullulate or reproduce themselves in the blood with inconceivable rapidity-not by seeds or spores, the usual method of reproduction in plant life, but by a process of fission or indefinite segmentation-and thus produce changes in the blood which usually result in sudden death, often without visible premonitory symptoms. After death has occurred the lowering of the temperature of the animal deprives the bacilli of the heat necessary to their existence; oxygen also fails them in the carcass, and they soon disappear from the blood. Moreover, the bacteria of putrefaction, which multiply with unusual rapidity in the carcass of an animal dead of anthrax, have a peculiarly destructive effect upon the bacteria of anthrax and increase the rapidity of the disappearance of the latter.

TWO FORMS OF ANTHRAX.

Two forms of anthrax occur according as the germ of the disease gains access to the blood through the abrasion of an internal membrane or of an external surface of the body. If by an internal abrasion, there results acute, apoplectic, or internal anthrax, which usually runs its course rapidly, often without visible external symptoms, until the animal is in the throes of death; if by an external abrasion, cutaneous, carbuncular, or external anthrax results, which usually manifests itself first by swellings in the vicinity of the abraded and infected spot, runs its course less rapidly, is more amenable to treatment in its early stages, and is somewhat less fatal than the internal form of the disease. In all other anthrax-infected countries internal anthrax has been observed to be by far most common, and their literature is devoted chiefly to this form. In Louisiana this order seems to have been reversed; the recent outbreak was due largely to external inoculation, and carbuncular or external anthrax was at least equally as common as the more fatal form.

SOURCES OF THE CONTAGION.

Since anthrax is but rarely communicated directly from one animal to another during life, the complete disappearance of the bacilli (the

sole cause of the disease) soon after death would seem to indicate that a particular source of contagion was forever removed with the death of each affected animal. But, on the contrary, another phase in the life of these parasitical plants makes the dead animal often a far greater source of danger than the living one; and this phase also accounts for the existence of the spores of the bacilli outside of the animal organism-that is, on soil, water, plants, etc.-where in infected localities they are a perpetual menace to animal life.

When blood containing these parasitical plants escapes from the animal, either before or soon after death, and is then removed from conditions of temperature and atmosphere favorable to their growth, the plants are exposed to the air and rapidly "go to seed;" the seeds or spores forming within the rod-shaped microscopical bodies of the bacilli much after the likeness of seeds in the pods of common leguminous plants. These spores, unlike the bacilli, are very retentive of vitality, very resistant to heat and cold, and will germinate or develop into bacilli again when taken into the animal organism, even after they have lain in the soil or upon other substances for years. By some authorities it is maintained that they will even go through their evolution in some kinds of soil, especially in soils rich in organic matter, but this is a subject of doubt. This sporogenous property of the Bacillus anthracis is the one to which is accredited the principal agency in the perpetuation of the disease; and, unfortunately, the conditions in nature favorable to spore formation are by no means rare. In the first place, it is a common symptom of anthrax that discharges of blood escape from the natural openings of infected animals, especially during the convulsions which usually attend their death. Pastures may become thus infected with the spores and remain for years a source of danger to other herbivorous animals. Again, the carcasses of animals dead of anthrax are frequently opened for postmortem examination, or for the purpose of making salvage of the hide or flesh, before the bacilli in the blood have lost their sporogenous property through putrefaction or a lowering of the temperature. It can readily be conceived how these common operations favor the perpetuation and spread of the contagion. Animals recently dead are often carelessly dragged across fields to out-of-the-way places, where their carcasses are left uncovered, and the contagion thus spread in obvious ways by carnivorous animals or rapacious birds; or they are thrown into streams or swamps, where the spores may again be taken into the systems of animals which come to drink, and whence the germs may even be carried by inundations and deposited on the vegetation of other lands.

The careless burial of animals is another fruitful source of infection. Earthworms may bring the spores to the surface from shallow graves, or the natural process of evaporation, especially in seasons of drouth on alluvial soil, may draw them up with the moisture. In

fact, so numerous are the opportunities presented for the formation of these pathogenic spores and for their dissemination over substances with which animals may take them into their systems, that anthrax would be the most devastating scourge known to the animal kingdom but for the limitations which nature has placed upon the invasion of the Bacillus anthracis and its spores into the animal blood.

The reports received by this Department from the infected parishes of Louisiana, almost without exception, attributed the extensive spread of anthrax there in 1896 largely to external inoculation by flies; and many inquiries were made with the sole object of ascertaining some substance that would be efficacious, when applied to animals, in keeping flies off their bodies. The swarms of these insects indeed constituted a veritable plague. There were many varieties, chiefly the blood-sucking sort; but to the Tabanus lineola, a small gray horsefly, was attributed the principal agency in disseminating the germs of the disease. It is notable that in foreign countries, although it is recognized that the fly may carry the germ of anthrax upon its feet or body from a diseased to a healthy animal, or may infect a healthy beast with its proboscis after having drawn blood from the infected one, yet few opportunities have ever occurred for extensively observing this method of infection. But in the lower Mississippi Valley inoculation by flies has long been regarded as an especial source of danger. In an outbreak in the State of Mississippi in 1889 it is recorded that swarms of a particular species of horsefly infested the infected districts, and attacked animals in such numbers as to leave upon the back, belly, and legs thick masses of clotted blood. This particular species was popularly believed to be the direct cause of the disease, instead of a mere medium of infection, and, therefore, became known as the "charbon fly." That flies also played an important part in the extensive dissemination of the disease in the recent epizootic in Louisiana, there seems to be no room for doubt; and it will be readily recognized how exceptionally an important factor this method of dissemination may be in the spread of this disease. It has been observed in all anthrax infected countries that the disease is usually confined to limited localities, sometimes to a single field where the germs have found lodgment and remain localized. The removal of animals from such localities is often marked by a cessation of attacks of the infection; or animals may even remain in the locality for a long time and only a few of them, possibly only one or two, may take the germs into their systems and contract anthrax. But where flies become common, active agents in the dissemination of the germs in an infected area, particularly flies in such swarms as appear in the lower Mississippi Valley in warm dry seasons, the disease is not likely to be limited to any defined locality, but to be spread over a territory limited only by the range of the flies.