December 20, 1889.] 



SCIENCE. 



417 



tions from the fresh juices aud tissues of animals dead of swine- 

 plague inoculations, the bacilli present an exquisite and typical 

 polar staining, unless the forms are very short, when the staining 

 is uniform. They are pathogenic for rabbits, mice, guinea-pigs, 

 pigeons, and bats. Two degrees of virulence in this organism 

 have been met. The one kind kills rabbits in from sixteen to 

 thirty hours, with enormous multiplication of the bacilli in the 

 blood and organs : the other kind destroys life in from two to six 

 days, occasionally longer, with extensive purulent and serous infil- 

 tration at the seat of inoculation, often with peritonitis, and with 

 frequently few bacteria in the blood and organs, but an immense 

 number in the inflammatory exudates. 



Regarding the distribution in the diseased hog of these two spe- 

 cies of bacteria, great variety exists, which cannot be fully de- 

 scribed in this short communication. In some cases the hog-chol- 

 •era bacilli have been found abundantly in the blood, intestine, and 

 all of the organs : in other cases they have been present only in 

 certain parts, most frequently the spleen and liver, and absent in 

 other parts. They may be absent from the spleen when abundant 

 elsewhere, as in the kidney. 



The swine-plague bacilli, when present, likewise vary in differ- 

 ent cases in their distribution. They are most frequently found in 

 hepatized areas in the lungs, but they may also exist in the intes- 

 tine, the blood, and various organs. 



As regards the frequency with which each of these organisms 

 has been found in the diseased hogs, the following groups of cases 

 have been met : first, herds of diseased swine, in which only the 

 hog-cholera bacillus has been found; second, herds in which only 

 the swine-plague bacillus was present ; third, herds in which both 

 the hog-cholera bacillus and the swine-plague bacillus were pres- 

 ent in the same animal, or the hog-cholera bacillus in some ani- 

 mals and the swine-plague bacillus in others of the same herd. A 

 few, chiefly scattered cases, in which neither the hog-cholera nor 

 the swine-plague bacillus was found, were met. 



Professor Welch and his co-workers have not been able to es- 

 tablish any constant anatomical differences between the cases in 

 which the swine-plague bacilli alone were present and those in 

 which only hog-cholera bacilli or both organisms were found. 

 While they have frequently found only the swine-plague bacilli in 

 -extensive hepatized areas in the lungs, they have also sometimes 

 found the hog-cholera bacilli alone in apparently similar pneu- 

 monias. They have not met any epizootic corresponding to the 

 German Schweine-Seuche in which pneumonia existed in any large 

 number of cases without intestinal lesions. 



With these results, they naturally looked with especial interest 

 to the effects of inoculation of healthy hogs with pure cultures of 

 •each of these organisms. The most stringent precautions were 

 taken in the selection and care of the experimental hogs. 



Two hogs, weighing about 75 pounds, not subjected to any pre- 

 liminary treatment, were fed each 225 cubic centimetres of bouillon 

 culture of hog-cholera bacilli. The one died in four and the other 

 in eight and a half days with extensive diphtheritic inflammation 

 and superficial circumscribed necroses of the large intestine, with 

 moderate swelling of the spleen and of the lymphatic glands, and 

 with ecchymoses in the lungs and elsewhere. Strongyles were 

 present in the bronchi, but there was no pneumonia. Hog-cholera 

 bacilli were found in abundance in the blood, intestine, and organs. 

 In a third hog 6.5 cubic centimetres of the same bouillon culture 

 were injected with antiseptic precautions into the duodenum. 

 Death occurred in seven days with the same lesions as in the pre- 

 ceding hogs. Two hogs exposed in the same pen with the first 

 hog were sick for a number of days, and gradually recovered. 

 These, when killed, presented undoubted evidence of the previous 

 -existence of acute diphtheritic inflammation of the large intes- 

 tine. 



The injection into the thigh and into the lung of 5 cubic centi- 

 metres of the same boufllon culture in two other hogs produced 

 ■only localized sloughs with slight constitutional disturbance. The 

 hogs were killed at the end of five weeks, and hog-cholera bacilli 

 were found alive in the sloughs, but none elsewhere in the body. 



The injection into the right lung of a pig of 8 cubic centimetres 

 of a pure bouillon culture of swine-plague bacilli was followed in 

 from forty-eight to sixty hours by death with extensive pneumonia, 



double fibrinous pleurisy, pericarditis, and peritonitis, and with 

 very abundant swine-plague bacilli in the exudates, the blood, and 

 the organs. Intestinal lesions were absent. The injection of 0.5 of 

 a cubic centimetre of bouillon culture of swine-plague bacilli into 

 each lung of another pig was followed by great rapidity and diffi- 

 culty of respiration, and coughing. The animal was killed at the 

 end of a week. Double sero-fibrinous pleurisy and pericarditis 

 and foci of pneumonia were found. The swine-plague bacilli were 

 present in abundance. The injection of pure cultures of swine- 

 plague bacilli with a fine hypodermic needle into the peritoneal 

 cavity was not followed by any manifest effects ; but in two cases 

 in which laparotomy was performed with antiseptic precautions, 

 and pure cultures of swine-plague bacilli (6.5 cubic centimetres) 

 were injected into the duodenum, the animals died in from sixteen 

 to thirty hours with acute diffuse peritonitis, pleurisy, and peri- 

 carditis, and an enormous number of swine-plague bacteria in the 

 exudates, blood, and organs, but without intestinal lesions. Doubt- 

 less some of the culture escaped into the peritoneal cavity. Sub- 

 cutaneous inoculations in two cases, and feeding in four cases, of 

 swine-plague cultures, produced no lesions, save localized abscesses 

 and sloughs after the injections. 



It is evident from these experiments that both the hog-cholera 

 bacilli and the swine-plague bacilli are pathogenic for svi'ine ; that 

 the former, when fed or injected into the duodenum, even in com- 

 paratively small quantity, are capable of producing intense diph- 

 theritic inflammation and necrosis of the large intestine with gen- 

 eral infection, and the latter, when injected into the thoracic cavity 

 or into the injured peritoneal cavity, of causing pneumonia and in- 

 flammation of serous membranes. 



If, as seems probable from these observations and experiments, 

 the hog-cholera bacilli are to be regarded as the cause of hog- 

 cholera, at least of the intestinal lesions, how is the failure to find 

 these bacilli in a number of cases of the disease to be explained } 

 A number of possibilities suggest themselves. First, the bacilli 

 may be confined to the intestine, and mixed with so many other 

 bacteria that it is difficult or impossible to isolate them. Their 

 morphology and the appearance of their colonies are so little 

 characteristic, that this might readily happen. That this, however, 

 cannot always be the explanation, is evident from the fact that in 

 several instances rabbits inoculated with typical necrotic buttons 

 have survived, and cultures and inoculations from other organs 

 have failed to reveal the bacilli of hog-cholera. Second, the bacilli 

 may be confined to the intestine, and so modified that they fail to 

 kill rabbits when inoculated subcutaneously. These bacilli appear 

 to vary somewhat in their virulence, and the possibility suggested 

 cannot at present be disproven. Third, as in cases of typhoid- 

 fever and croupous pneumonia in human beings, the specific bacilli 

 may disappear in the later stages of the disease. This explanation, 

 which is suggested in the reports of the Bureau of Animal Indus- 

 try, seems probable, but, as already mentioned, the investigators 

 have not been able to distinguish anatomically cases in which hog- 

 cholera bacilli could not be detected from some of those in which 

 they were present. 



It is not clear to them what ro/e is to be assigned to the swine- 

 plague bacilli in the natural infections which they have studied. 

 The facts that experimentally the swine-plague bacillus is capable 

 of causing extensive pneumonia and inflammations of serous mem- 

 branes, and that epizootics occur in swine in Germany with these 

 as the predominant lesions without intestinal disease, suggest that 

 this organism, which is apparently identical with that of the Ger- 

 man Schweine-Seuche, is also the cause of a similar affection in 

 this country. They are not, however, aware that any swine epi- 

 zootic of pneumonia without any intestinal lesions, and with the 

 sole presence of the swine-plague bacillus, has been observed in 

 this country, although cases of this description occur scattered in 

 epizootics of hog-cholera with intestinal lesions. Until such an 

 epizootic is observed in this country, it is not likely that the question 

 will be thoroughly elucidated as to the ro/n of the swine-plague 

 bacilli. It is possible that the swine-plague bacilli are frequently 

 present in the mouth, the air-passages, or the intestine of healthy 

 hogs, analogous to the frequent presence of the micrococcus of 

 sputum-septicsemia and of pneumonia in the mouth of human 

 beings, and that in the mixed infections which have been observed 



