EEPOBT OF THE BUKEATJ OF ANEVIAL INDUSTEY. 101 



there were lesions of the large intestine, of the character of an exu- 

 date, of a partly croupous, partly diphtheritic character. In the two 

 succeeding. (Nos. 408, 409) there were ulcerations, shallow but ex- 

 tensive, differing from the.ra.ore penetrating hog cholera ulcers. In 

 the remaining cases (excepting No. 396) the intestinal lesions con- 

 sisted of extravasation, pigmentation, and ulcers which were very 

 likely hog cholera ulcers. In No. 396 the croupous exudate pre- 

 ponderated. 



As regards the bacteriological examination, the first case (No. 406) 

 was not examined. Of the remaining fourteen, nine contained swine 

 plague bacteria. These were obtained either directly from the pleural 

 exudate or from rabbits and mice by inoculating them from the dis- 

 eased lung tissue. Of those from which no swine plague bacteria 

 were obtained it will be noticed that the lung disease was far ad- 

 vanced. The lung tissue was either converted en masse into a 

 homogeneous mass like cheese, or else the latter was sprinkled 

 through the lung tissue in smaller masses. It must also be remem- 

 bered that the absence of swine plague bacteria should not be in- 

 ferred from the inoculation of a minute quantity of diseased lung 

 tissue. It seems, however, very probable that in this advanced stage 

 of degeneration the original pathogenic bacteria have been in greater 

 part destroyed. In the later cases (Nos. 409, 372, 397, 396, 392, 366) 

 hog cholera bacteria were also present, as determined by culture and 

 inoculation experiments. 



How can we interpret these results ? Swine plague in a very acute 

 form had attacked the herd, and in earlier cases this disease appeared 

 in an acute uncomplicated form. This is indicated by the peculiar 

 intestinal lesions (Nos. 402, 403, 405, 407). The two succeeding cases 

 (Nos. 408, 409) were more advanced and less severe; the intestinal 

 ulcers, shallow and broad, were the result of the diphtheritic exudate, 

 which had passed away. The lung tissue was in part dead. In the re- 

 maining cases the characteristic swine plague lesions disappeared from 

 the intestine, and the lungs showed a more advanced state of cheesy de- 

 generation. The progress of the disease from a very acute to a chronic 

 form, due most likely to a gradual degeneration of the virulence of the 

 bacteria, is thus very well illustrated. In these later cases hog cholera 

 bacteria are found in the spleen, and more rarely in the thoracic 

 organs. The last cases died of acute hog cholera, with lungs normal. 

 The exact part which the hog cholera bacteria played in the last 

 swine plague cases can not be formulated. It seems to me that they 

 were an attenuated variety which found a place in the organisms 

 because the latter were diseased, and that they grew in virulence 

 until they were able to produce (a month later) the acute hemor- 

 rhagic form of this disease. There seems to be nothing so convincing 

 of the gradual increase and decrease in the virulence of these two 

 species of bacteria as the careful observation of a single epizootic 

 from the beginning to the end. The mechanism of this change of 

 virulence is important enough to warrant prolonged study. 



There were a few cases that deserve special mention. Nos. 405 and 

 407 (Plates I, II) were perhaps the most typical of the acute, un- 

 complicated form of the disease. No. 410 is instructive, in that the 

 disease seems to have spent its force chiefly upon the skin, leaving 

 the lungs comparatively intact. The large size of this animal (the 

 largest that died) may perhaps account for .the shifting of the dis- 

 ease to the skin. 



