DISEASES OF SWINE AND OTHER ANIMALS. 379 
that the blood, the channel through which these must be carried to the 
various organs in which they are found, must prove virulent. One of 
Dr. Klein’s experiments appears to negative this conclusion, whereas 
three of mine go to support it. From what we know of the generation 
of microphytes, it seems not improbable that at certain stages of its de- 
velopment this specimen may fail to be injurious, or more probably the 
germs may be filtered from the blood, being arrested in the capillaries, 
where they determine the morbid changes, and thus many specimens of 
blood may be obtained which are destitute of the morbid element, until 
that is again produced in abundance by proliferation in the tissues. By 
reference to my experiments, it will be seen that the blood with which 
the successful inoculations were made was taken from pigs in the last 
stage of the disease, or just after death. That the blood is virulent at 
-certain stages is unquestionable, and in the nature of things this can 
scarcely fail to be the case, even if we were to set aside experiments and 
reach our decision from the lesions alone. 
CAUSES. 
It has been no part of my purpose to investigate the causes of this 
disease apart from the one specific cause of contagion. It was indeed 
impossible to pursue such a line of inquiry at a distance from any dis- 
trict where hogs are largely raised, where the disease prevails exten- 
sively, and where, presumably, new generations of the poison are taking 
place. One instance, however, of probable generation de novo has been 
brought under my notice, and the attendant circumstances were such 
that I think it important to publish the principal facts. In the end of 
April, 1871, Colonel Hoffmann, of Horseheads, purchased a large herd 
of swine to consume the buttermilk of his creamery. The swine were 
supplied with sheds, the open range of an orchard, with plenty of shade 
under the trees, on a gravelly soil, rising abruptly 10 to 15 feet above 
the general level of the valley, and were fed fresh buttermilk and corn 
meal. Ail went well until late in June or early in July, when the hogs 
began to sicken and died in large numbers, with the general symptoms of 
the hog fever. Ihave mentioned this mainly to negative the widespread 
belief that the source of the trouble is, in the exclusive feeding upon 
corn. Here we had a laxative and otherwise model diet, supplemented 
only to a slight extent by corn. It may be well to state that in other 
years, when he has purchased Western hogs, the disease has always 
appeared within ten days or a fortnight after their arrival. When New 
York State hogs only have been bought the pestilence has not broken 
out. 
In view of the strong assertions that pigs will not contract the disease 
when fed in part on green food or on succulent vegetables—turnips, 
beets, potatoes, apples, &c.—I had some subjects of experiment freely 
supplied with potatoes and apples, but whenever the poison was intro- 
duced by inoculation I could detect no difference in the period of incu- 
bation or the severity of the attack. . 
It may be added that all unwholesome conditions of feeding and man- 
agement will favor the development of this as of other specific fevers, 
by deranging the nutrition, disturbing the balance of waste and re- 
pair, loading the blood and tissues with effete and abnormal products, 
raising the body temperature, and on the whole bringing about a state 
of the system extremely favorable to the propagation and growth of 
disease germs. But while the importance of all these may be recog: 
