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of these two maladies and to determine whether they do not frequently exist in the same localities.

The microbe from Iowa outbreaks showed a greater virulence, as a few drops of culture fluid were sufficient to destroy mice and rabbits in less than twenty-four hours. Whether such differences are sufficient to account for the varying severity of the disease in different localities remains to be determined by more extended observation. The fact that the subcutaneous inoculation of cultures did not affect two pigs may be due to a want of power to develop in the internal organs. This is virtually the case in the disease, as it appears naturally among swine. Though the lungs may be extensively diseased, the blood, spleen, and other internal organs are practically free from bacteria. The disease seems to be caused by inhaling or aspirating the specific bacteria, which exert their destructive effect in the alveoli and smaller bronchi, and do not in reality enter the blood of the affected animal. The final test will rest upon the possibility of producing the specific lung disease by means of inhalation experiments which are now being carried on.

RECENT FOREIGN INVESTIGATIONS IN INFECTIOUS SWINE DISEASES.

The investigations by foreign observers during the past year upon infectious diseases of swine, and more especially their causation, have led to some interesting results, which deserve careful consideration. In the Second Annual Report of this Bureau it was pointed out that the disease known in this country as swine-plague, or more commonly as hog-cholera, was wholly different from the disease known on the Continent as rouget and Rothlauf. Not only are the lesions different, but the micro-organisms producing them wholly unlike in their microscopical and biological features, as well as in their pathogenic effect upon animals. Thus far rouget has not been found in this country. The conclusions reached last year, though doubted by those who seemed to consider all infectious or contagious diseases of swine identical, are unshaken. All efforts at practicing preventive inoculation in hog-cholera with virus derived from rouget must not only be looked upon as absurd in the light of present knowledge, but as dangerous, inasmuch as a new disease may thus be introduced into our country from abroad.

The important lesson taught by these investigations lies on the surface. Infectious diseases in which the gross pathological effects differ quite constantly in the same species of animals should not be classed as identical until so proved by the most rigorous methods that scientific research possesses.

On page 226 of the Second Annual Report of the Bureau (1885) a brief mention was made of a disease found once by Löffler in Germany, which presented as the most marked lesion an enormous oedema or swelling of the skin of the neck. It is caused by small ovid bacteria, calling to mind by their appearance the organisms of septicæmia in rabbits, especially when in the process of division, although but half as large. Inoculation with these bacteria produced speedy death in rabbits, mice, and guinea-pigs, as well as pigs. Rabbits died within twenty-four hours; mice lived a few hours longer; guineapigs died on the second and third day after inoculation. In all animals there was a sero-sanguinolent effusion into the subcutaneous tissue of the entire abdomen, extending to the axilla on the one hand and the inguinal region on the other. Muscular tissue infiltrated

with the same reddish effusion. Pigeons, fowls, and rats remained unaffected after the inoculation. One of the three inoculated pigs died on the second day with the following lesions: "Skin of abdomen bluish red. Enormous cedema of the skin. Lungs hypostatic. Mucosa of stomach deeply reddened. Spleen unchanged. Kidneys parenchymatous. Mesenteric glands not swollen."*"

More recently this same infectious disease among swine in Germany has been carefully described and studied by Schutz, and as it has many features in common with the disease which has been separated from hog-cholera in the preceding pages, it deserves a somewhat careful analysis here.

The author first obtained the microbe causing this disease by placing beneath the skin of small animals bits from spleens of pigs which had presented symptoms of rouget. The spleens were putrid, but the pathogenic microbe was found alone in the bodies of the inoculated animals, the putrefactive germs not having the power of penetrating beyond the wound in which they are placed. In this way he inoculated 2 mice, 2 guinea-pigs, 1 pigeon, and 1 rabbit. The mice died on the second and third day. The bacteria found in the organs of these mice have the form of ovals, and are easily stained by watery solutions of aniline colors.

When stained with gentian violet they show in their central portions an unstained region surrounded by a layer stained blue. The thickness of this layer is greater at the poles, so that the extremities appear more deeply stained than the sides. When deeply stained they appear uniformly blue. As these organisms stand between microcococci and bacilli, they may be called bacteria. They are 1.2mm long and .4mm to .5mm broad. They multiply in the following manner: They become twice as long as broad, show distinctly rounded extremities, and stain like the organisms of rabbit septicemia and fowl-cholera, so that between the deeply stained ends about one-half or a third of the entire length remains unstained. Careful examination shows, however, that the colored end pieces are connected with each other by a fine line which passes from one to another on each side. The end pieces then separate and the median portion disappears. The former are at first spherical, but very soon assume an oval form. Hence from every organism two new individuals arise by division, in which by careful staining the uncolored central portion is easily distinguished from the colored periphery. If the process of multiplication is very rapid, as in pigs and rabbits, the organisms do not attain the size given above, but divide before the unstained median piece becomes distinctly visible. Under these circumstances the organisms of the succeeding generations are smaller, only one-half as large as, or even smaller than, those which have resulted from the slow division of the bacteria. The younger generations are frequently extraordinarily small, plainly oval, however, and staining uniformly in gentian violet. * They do not execute any spontaneous movements.

This description applies very well to the microbe found by us in pigs with lung disease. It points out the folly of expecting to determine a specific form with the aid of a microscope and an aniline. stain only, when we reflect how many different forms of one specific microbe may be met with, according to the rapidity of multiplication, which in turn depends upon the medium in which they grow.

We will continue with the author's statement. The rabbit died on the third day. From the inoculated ear an inflammatory swelling had spread over the entire head and neck, due to an extensive effusion of a turbid liquid into the subcutaneous connective tissue. Enlargement of neighboring lymphatics. Bacteria in the blood and all

* Arbeiten a. d. kaiserlichen Gesundheitsamte, I, S. 377. Loc. cit. S. 376.

The bacterium of hog-cholera as found in Nebraska was obtained pure in the same way as described elsewhere in this report (p. 623).

organs, especially numerous in the subcutaneous effusion. The two guinea-pigs and the pigeons remained well. Gelatine tubes inoculated with this germ show no signs of liquefaction at any time. With a pure culture on gelatine the author inoculated two mice, one rabbit, and three pigeons. The mice died on the first and second day after inoculation respectively. The lesions were as follows: "Slight œdema and hyperæmia of the subcutis. Swelling of the lumbar, inguinal, and mesenteric lymphatic glands. Large intestine filled with feces; spleen considerably enlarged. Parenchymatous inflammation of liver, kidneys, heart, and muscles. Portion of blood coagulated; the remainder coagulates on exposure to air. Bacteria in all the organs." The rabbit died on the second day after inoculation. Besides local and general lesions already mentioned, there is an implication of the respiratory apparatus (tracheitis and bronchitis hemorrhagica). To these lesions we cannot attribute any specific character whatever. They are very likely due to proximity to the point of inoculation (ear). If the animal had been inoculated in the thigh they might have been absent. The pigeons remained well.

Two pigs were inoculated with beef-infusion peptone culture, obtained from a mouse, each receiving subcutaneously the contents of a Pravaz syringe. On the following day a considerable tumefaction of the thigh appeared. The skin over the swelling was dark red. Both animals were so weak as to be scarcely able to walk. No appetite. Breathing accelerated. One of them died twenty-four hours after inoculation. At the autopsy the following changes were observed: Infiltration of skin, connective and muscular tissue at the point of inoculation, with a red turbid effusion; the skin tough and thickened. About 55cc of turbid yellow liquid in the peritoneal cavity. The other changes given by the author do not point to any specific lesions, and are omitted. The bacteria were found in the exudates and in all the organs, especially numerous in the effusion at the point of inoculation. The other pig died forty-eight hours after inoculation. In this animal the local swelling was also very extensive and severe. Bacteria in all the organs.

The lesions indicated that the bacteria had at first multiplied and exerted their pathogenic effect at the point of inoculation, and thence had spread over the entire body by way of the blood and lymph channels.

The author calls attention to the great resemblance between the inoculation disease produced by him and by Löffler, and considers the cause the same in both cases.

A pig which had been made insusceptible to rouget by vaccination was inoculated with a pure culture of this oval bacterium. It died in two or three days, with extensive local swellings where the inoculation had been made. Bacteria in all the organs; especially numerous in the spleen. This case illustrated the fact that an animal made insusceptible to one disease is not necessarily protected against the virus of another.

Schütz was unable to produce the disease by feeding, as the following shows: After starving a pig for twenty-four hours it was fed with bouillon in which 5 per cent. sodium carbonate was dissolved, and half an hour later with one liter of blood and pieces of flesh from a pig which had succumbed to inoculation. The animal seemed slightly ill for a few days, but recovered.

In continuing these investigations an epidemic came to his notice in which the early symptoms were diarrhea, sometimes bloody. At

the same time the hind legs became stiff, so that the animal lay most of the time. On the sixth and seventh day the back became weak, so that in walking the animals swayed to and fro. They then were scarcely able to reach their food without tumbling over. In a few the ears became red. In all the breathing became labored and hurried. In some twitching and convulsions appeared before death, which occurred on the eighth to the tenth day. Without giving the complete autopsy notes it will suffice to say that there was nothing abnormal in the intestinal tract. The stomach was considerably bile-stained. The lesions were limited to the thoracic cavity. In the pericardial cavity about 36 grams of an opaque reddish fluid. Pericardium and epicardium glued together by small quantities of a warty, stringy, elastic substance:

* *

Both lobes of the left lung, with the exception of the upper border and the four lobes of the right lung, tough and airless (hepatized). In both pleural sacs about 64 grams of an opaque reddish-yellow fluid, mixed with flakes of fibrin. The pleura covering the hepatized portions was rough, dull, clouded. These were in general of a dark grayish red, with interspersed, circumscribed patches of various size and form and grayish-yellow or reddish-yellow in color. *On the cut surface of the hepatized portion grayish-red and reddish-yellow areas could be detected, which were sharply marked off from one another. They corresponded to the circumscribed patches on the pleura, were very friable, partly with a pale luster, partly granulated. They occupied larger volumes of lung tissue, or were sprinkled as scattered foci in the grayish-red portions. Their extent was limited by the course of the larger bronchi and blood vessels. The surface of the grayish-red portions was also granulated, of a faint lustre, and clouded. In these there appeared numerous, more resistant, reddish-yellow spots, corresponding to the inner portions of the lobules. They were either isolated or gathered into small groups. The interlobular tissue was filled with a cloudy reddish fluid. In the softer portions of the lung the pleura was smooth, transparent. The cut surface was smooth, shining, and here and there provided with small diffusely dark red spots; resistant. On compression a very fine foam poured out upon the cut surface. The bronchial lymphatics were enlarged, their capsules reddened.

In a second animal the lesions were the same, almost the whole lungs hepatized. These animals had therefore suffered from an acute pleuro-pneumonia, involving the pericardium in the first animal. The yellow regions correspond to necrosed tissue, which, extending to the surface, produces inflammation of the pleura. In cover-glass preparations of the lung tissue the oval bacteria were found in large numbers. The author infers from the lesions that the bacteria had been aspirated into the finest bronchioles and alveoli and there produced pneumonia. They were also found in the pleural and pericardial cavities. The remaining internal organs contained but few. With portions of the hepatized lungs six mice, five guinea-pigs, two rabbits, two rats, two pigeons, and one fowl were inoculated. The mice and rabbits died in the usual time, and presented lesions already described. Three of the guinea-pigs died on the fourth, fifth, and eighth day respectively. In the two first mentioned the subcutis and muscular tissue at the point of inoculation (abdomen) were infiltrated with a bloody, clouded liquid; in the third animal-an old one-an extensive hemorrhagic and purulent infiltration was present. One of the pigeons died on the third day. The point of inoculation in the subcutis over the pectoral muscle was infiltrated with a fibrinous, purulent mass, containing a few bacteria. These were very scarce in the internal organs. One of the rats died on the seventh day with lesions similar to those of the older guinea-pigs. Very few bacteria in the internal organs. With bits of lung tissue from another pig H. Mis. 156-7

which succumbed to the same infectious pneumonia the following animals were inoculated: two rabbits, guinea-pigs, pigeons, and fowls, and one rat. The rabbits died in one day, the guinea-pigs in two and five days respectively after inoculation. The two pigeons, which had received comparatively large doses, died in one and two days respectively. The rat and fowls were not affected.

The author also introduced pure cultures directly into the lung tissue of a pig through the chest-wall by means of a hypodermic syringe. The animal died in less than three days. On post mortem examination the lungs were necrosed at the point of inoculation; there was severe and extensive pleuritis and pericarditis. Bacteria were very numerous in the affected organs, but very scarce in other organs. In another experiment a pig confined in a box was made to inhale the spray of a liquid culture for several hours on two consecutive days until 500cc had been used up. The animal was killed eleven days later, after having shown marked symptoms of lung disease. The same mortifying pneumonia as that described was found at the autopsy.

Schütz also describes a case in which there was a condition of the lungs, lymphatic glands, and other organs closely resembling tuberculosis. Caseous degeneration of these structures was followed by a gradual loss of strength, leading to death. In this animal there was a caseous degeneration of the various joints of the posterior limb, enlargement and softening of the lymphatics. The oval bacteria were present in large numbers in the caseous contents of the glands. The effect upon small animals when inoculated with this caseous mass was precisely the same as that produced by lung tissue or cultures from former cases.

The disease disappears at the beginning of winter to reappear again in the spring. The losses sustained by one owner from the disease in a single year were very heavy, two hundred pigs having died. It was found in regions a considerable distance apart, which led Schütz to infer that it was a widely distributed disease.

The relation of hog-cholera to this disease.-A careful perusal of this brief synopsis will convince even those who have only observed the gross pathological lesions that are constantly met with in hog-cholera, or who have read the post mortem notes as reproduced and summarized in this and the preceding report, that this new disease described by Schütz has nothing in common with hog-cholera. We regard the description of the disease as given in these reports as the basis for this statement, because the hundreds of cases examined in the laboratory were invariably associated with the same etiological factor-the same bacterium which has been minutely described, and which is at once distinguishable from the microbe described by Schütz. Leaving aside the many differences, a glance into the microscope will show us an actively motile bacterium on the one hand, and on the other a non-motile bacterium. Our investigations have already shown the existence of another bacterial disease in swine, which may even be associated with hog-cholera, in the same herd and in the same animal. From the present standpoint of our information it would be presumably absurd to rely upon post mortem examinations in different parts of the country without at the same time making bacteriological investigations, in order to decide the nature of a certain class of symptoms and lesions. We have almost invariably found severe intestinal lesions in hog-cholera, producing ulcera

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