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506 REPORT OF THE COMMISSIONER OF AGRICULTURE, 
succeeding (Nos. 408, 409) there were ulcerations, shallow but ex- 
tensive, differing from the more 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. Phi: 
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 | 
waxy 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 
art destroyed. In the later cases (Nos. 409, 372, 397, 396, 392. 366 j 
og 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 (tos. 403, 402, 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 disappear from | 
the intestine, and the lungs show a more advanced state of cheesy de- 
generation. The progress of the disease from a very acuteto achronic 
form, due most likely to a gradual degeneration of the virulence of the 
bacteria, is thus very well illustrated, In theselater 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. Now 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 foree 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. 
The introduction of hog cholera after the appearance of swine 
plague was most likely due to the case first reported in these pages 
(No. 406). 
