INVESTIGATION OF SWINE PLAGUE.

INTRODUCTORY.

In the further investigation of swine plague Dr. Detmers finds but few additional symptoms worthy of mention. As his observations extended through the winter he was enabled to observe the disease closely during those months when it is neither so general nor so fatal as during other seasons of the year. During the winter months, therefore, and in the early spring, he found bleeding from the nose and symptoms of respiratory disorders quite frequent, but there seemed to be fewer indications of gastric disorders than he had observed during the summer and fall months. Neither was the prognosis, as a rule, so hopeless in the winter and spring as during the summer and early autumn. This he regards as attributable to the fact that during the former seasons the seat of the morbid process is limited more frequently to the respiratory organs and to the pulmonal tissue, and is not found so often in the intestinal canal. Thirty additional post-mortem examinations failed to reveal any new morbid changes worthy of special mention. A few variations, and in some cases an unusual combination of morbid changes, were observed, which will be found accurately described in the text of Dr. Detmers' report. The absence of worms or entozoa in 75 per cent. of the whole number of animals dissected prior to December 1, and their entire absence in every animal examined between that date and the 15th of the same month, would seem to prove conclusively, Dr. Detmers thinks, that the morbid changes characteristic of swine plague cannot be attributed to the work of entozoa. He thinks, however, that the presence of worms in large numbers, occurring in weak, poorly-kept, and neglected animals, may cause considerable mischief, and sometimes occasion death, but in such cases the cause should not be attributed to swine plague.

Former experiments seemed to fully demonstrate the fact that swine plague is an infectious and contagious malady, and that it is easily communicable from one animal to another by means of direct inoculation, and by the introduction into the digestive organs of the infectious principle by means of food and drinking water; second, that an exceedingly small quantity of the virus or infectious principle is sufficient to produce the disease; third, that the period of incubation does not exceed fifteen days, and lasts on an average from six to seven days; fourth, that the small microphytes (bacilli) found in all the morbid products, in the blood and other fluids, and in all excretions of the animals, would seem to constitute the infectious principle of the malady. This being the case Dr. Detmers instituted a series of experiments in order to determine, if possible, first, whether the infectious principle consists solely in the bacilli and their germs; second, whether an animal that has recovered from the disease has gained immunity from a second attack; and, third, whether the affection can be transmitted to other classes of domesticated animals. The result of these experiments proved, first, that an inoculation with bacilli and bacillus-germs cultivated in so innocent a fluid as milk will produce the disease with just as much cer tainty as an inoculation with pulmonal exudation from a diseased or dead hog; second, that an animal that has been afflicted with the plague

has not lost its susceptibility, but may contract the disease again, though probably in a milder form.

In order to test the susceptibility of other animals to the contagion, Dr. Detmers inoculated two heifers with the virus of swine plague, and the elevation of temperature and the subsequent post-mortem examination would seem to indicate that the disease prevailed, at least in one case (heifer No. 2), to a considerable degree of intensity. The autopsy revealed distinctly limited (circumscribed) hepatization at several points in both lobes of the lungs, each single patch comprising only a few lobules, but these were distinct and well defined. The most extensive hepatization was found along a larger bronchus in the posterior part of the left lobe. The hepatized parts or patches amounted to about 4 or 5 per cent. of the whole pulmonal tissue. The mucous membrane of the bronchia was found to be slightly swelled; a small quantity of serum was found in the pericardium and in the chest, and a few ounces also in the abdominal cavity. The lymphatic glands of the chest, and those belonging to the mesenterium, were enlarged, and some of them, especially the latter, to a considerable extent. The other organs exhibited no abnormal changes. The result of this experiment indicates that while cattle are not as susceptible to this plague as swine, yet it may be transmitted to them, in a mild form, by direct inoculation.

Many illustrations are given of the manner in which the contagious principle is transmitted from herd to herd and from farm to farm. Believing that the seeds of the disease consist in the bacilli and their germs, as fully described in his former report, Dr. Detmers is of the opinion that these microphytes can be conveyed from one place to another, not only in the morbid products of the disease, such as the tissues, fluids, and excretions of affected and dead animals, but also by adhering to and contaminating inanimate objects, both fluid and solid, and independently of any vehicle, through the air to a distance of a mile if the conditions are favorable, and in the water of running streams. The last mode is one of the most prolific sources of infection, as these microphytes propagate and multiply in water, especially if it should be contaminated by a mixture of organic matter. After citing many cases in illustration of the various ways in which the contagion is spread, Dr. Detmers is of the opinion that the following facts have been established:

First. The plague is not easily communicated unless the infectious principle is introduced either into the digestive apparatus with the food or with the water for driuking, or directly into the blood through wounds, sores, scratches, or external lesions.

Second. That the carcass of an animal that has died of the plague will communicate the disease to healthy swine if eaten before it is thoroughly putrified.

Third. That even severe frost is not sufficient to destroy the infectious principle if the same is protected against external influences by some organic substance. Former experiments by Dr. Law also demonstrated this fact.

Fourth. That the plague is readily and frequently communicated to healthy animals by means of the water used for drinking, especially if the same should be contaminated by the carcass of an animal that has died of the disease, or by the excrements, urine, nasal discharges, saliva, &c., of animals afflicted with the malady.

Fifth. That in localities where the plague is prevailing, every wound, scratch, or sore on the surface of the body constitutes a port of entry for the infectious principle.

Sixth. That old straw stacks and other decaying porous bodies may

preserve the infectious principle for months, and in many cases even for a whole year.

Seventh. That the infectious principle enters the animal organism and communicates the disease more readily through external sores and lesions than through the digestive canal.

Many experiments were instituted for the purpose of determining upon a system of preventive measures and of testing the value of certain remedial agents. As to the result of these experiments and the conclu sions deduced therefrom, the reader is referred to the detailed report of Dr. Detmers.

When Dr. Law closed his former report he had just commenced some important experiments for the purpose of determining the susceptibility of other animals to swine plague. These experiments resulted, as he had previously foreshadowed, in the successful inoculation of sheep and rats, and in the transmission of the disease from these animals back to swine in a virulent and intensified form. His first experiment was undertaken for the purpose of determining at what period or stage of the malady it is most easily and certainly transmissible from one animal to another by cohabitation. In his previous report an experiment of this kind was furnished, and a deduction made that the disease was most virulent when at its height, inasmuch as the exposed pig seemed to resist the contagion from an animal in process of convalescence, but within twelve days fell a victim to the disease when placed alongside of a pig in which the malady was rapidly advancing. In the accompanying report the necropsy of this pig is given, from which it will be observed that it was afflicted with the plague in an intensified form.

The autopsy of an infected lamb, noticed by Dr. Law in his former report, is also given in full. The intestinal irritation and catarrh, shown in the tenderness of the anus and the mucus discharges accompanying the feces, together with the elevated temperature and large lymphatic glands, presented much in common with the affection in the pig. The marked eruption in the ears might be accepted as representing the skin lesions, so common in swine suffering with the plague. The more characteristic lesions revealed by the post-mortem examination were the purple mottling of the liver, kidneys, and heart, the grayish consolidation of portions of the lungs, and the deep pigmentation of the lymphatic glands in general.

The next experiment was that of a merino sheep infected by inocula tion. The record and the results of the autopsy are very similar to those furnished by the lamb. Here, again, the principal changes consisted in purple mottling of the liver and heart, and the deep pigmentation of the lymphatic glands. Dr. Law is of the opinion that the yellowish-brown coloration of the kidneys in this case implied antecedent changes, probably of the nature of inflammation or extravasation.

From virus taken from these animals Dr. Law successfully inoculated a pig. The pig was inoculated twice, at an interval of fifteen days, with mucus from the anus of the infected sheep, and with scabs from the ear of the lamb. Enlarged lymphatic glands were observable before the last inoculation, and six days after there was a febrile temperature and the more violent manifestations of the malady. The following characteristic lesions were revealed by the necropsy, viz: The intestines contained patches of congestion; the follicles were enlarged, and the rectum ulcerated; purple discolorations were present in the liver, kidneys, and heart; the lymphatic glands were enlarged and congested by a deep red, in some cases almost black. While the evidence of the presence of the disease in this case was quite positive, in order to confirm