KEPOBT OF THE BUREAU OF ANIMAL INDUSTBY. 107 



cysticerci. There was a small, softened, whitish mass in the muscles of the thigh 

 at the place of inoculation. The second rabbit, perfectly well up to the twenty- 

 fourth day, was then inoculated on both ears with a bit of lung tissue from swine 

 plague, to which it succumbed in a few days. 



Cultures of this microbe were injected beneath the skin, into the thorax, and into 

 the trachea of pigs without causing any disturbance. It therefore had but slight 

 pathogenic properties, and no further attention was paid to it. It may be that it 

 is the streptococcus pyogenes found occasionally in abscesses. 



In some cases when the powers of life are much reduced and the 

 destruction of the lungs is far advanced, the same bacteria which are 

 found entering the pleura! cavity may appear in the blood, spleen, 

 and other organs. This was true of No. 392, in which the chromo- 

 gene there mentioned was found in the spleen as well as in the pleu- 

 ral cavity. In a considerable percentage of the cases given, anaero- 

 bic bacilli were found in the cultures from the internal organs. These 

 microbes may have gained entrance by way of the digestive tract 

 (liver) or the diseased lungs in the form of spores and developed un- 

 der the peculiarly favorable conditions. Death usually takes place 

 by a paralysis of the respiratory function (asphyxia) ; the right ven- 

 tricle and large vessels are filled with large thrombi. The system 

 being thus slowly but completely deprived of its oxygen anaerobic 

 bacteria may multiply and appear in cultures. They seem to be bu- 

 tyric bacilli, judging from the odor emitted by the cultures. These 

 bacilli carry on a feeble existence in the lowest strata of liquid cult- 

 ures and die out very soon. 



The presence of the bacterium of swine plague in animals having 

 hepatized lungs has been proved in several outbreaks, some of which 

 have been dwelt upon in the preceding report of the Bureau. They 

 may be summarized briefly as follows : The specific microbe was ob- 

 tained from the spleen at Geneseo, 111., July, 1886; from the pleural 

 cavity (as a pure culture) of a pig at Sodorus, 111., September, 1886; 

 from lung tissue (by inoculation into rabbits) sent from Iowa, Jan- 

 uary, 1887; from a considerable number of cases fully described in 

 this report, studied at the experiment station of the Bureau during 

 the winter of 1887. In all of these cases hepatization of the lungs 

 was present. This organism has never been obtained in cultures 

 from several hundred cases of hog cholera in which extensive lung 

 disease was absent. 



The final proof of the causal relation between a given microbe and 

 a disease having definite pathological characters can only be brought 

 by actually reproducing the disease in healthy animals with pure 

 cultures of the given microbe. 



In the experiments made with this in view, and detailed in the pre- 

 ceding pages, cultures were introduced into the lungs through the 

 trachea, and pigs were exposed to the spray of liquid cultures. In 

 none of these experiments was the disease reproduced. In two cases, 

 however, the injection of a few cubic centimeters of culture liquid 

 into the thorax produced large abscesses, the contained pus being of 

 a semi-solid caseous consistence. The presence of the injected bac- 

 teria in immense numbers proved them to be the cause of these 

 changes. These two cases are by no means positive, but very pre- 

 sumptive evidence that the microbe under consideration is the true 

 cause of swine plague. 



There are several reasons why this microbe may not produce the 

 disease when introduced into the.luiigs b,y way ( of the -trachea. There 

 may be a rapid attenuation in artificial cultures. But more plausi- 

 ble than this is the theory that in this, as in perhaps the great ma- 



