- - vt 
DISEASES OF SWINE AND OTHER ANIMALS. 407: 
DR. LAW’S SUPPLEMENTAL REPORT. 
As an addendum to my former report, I would respectfully submit the following 
| further observations on the fever of swine, commonly known as hog cholera: 
4 EXPERIMENTS IN FEEDING THE VIRULENT MATTER. 
A healthy pig was fed the substance of an intestinal ulcer and a little manure from 
the same bowel, but showed no evil results for fourteen days, when it was put to 
; other uses. It should be added that the ulcer fed to this pig was partially putrid, 
and was inoculated on two other swine without success. 
A second pig was fed a portion of dried intestine and its contents, both ef which had 
remained packed in wheat-bran for a month. Notwithstanding this, the animal re- 
tained good health for seventeen days, when it, too, was put to other uses. The 
material fed to this pig acted with fatal effect on two other pigs on which it was in- 
oculated. 
These experiments can only be taken as showing that a small quantity of poison 
may pass through the intestinal canal with impunity, but they would not warrant 
the conclusion that similar materials would be equally harmless when taken in larger 
quantities and with every meal, as invariably happens when swine are fed in the ordi- 
} nary manner and plunge their filthy feet and noses fresh from the pestiferous manure 
| into the feeding-trough. Dr. Osler has succeeded in developing the disease by feeding 
- the diseased intestine, but as the feeding was accomplished by force there is just the 
possibility of abrasion and directinoculation. Abrasions are indeed so common in the 
i” mouth from injuries by the teeth and by hard objects masticated and derangements of 
the epithelial covering of the mucous membrane of the stomach and intestines, are 
so frequent in connection with slight gastro-intestinal disorders, that it is needless to 
ealeulate on an immunity which can only be secured by the entire absence of such 
lesions. If to secure immunity in feeding we must provide that not even a worm shall 
bite the mucous membrane of the stomach or intestine, any guarantee rests on an ex- 
ceedingly slender basis and had best be rejected at once. 
SUCCESSFUL INOCULATION WITH FROZEN PRODUCTS OF THE DISEASE. 
In two cases I have successfully inoculated virulent products which had been frozen 
hard for one and two days respectively. In both instances the resulting disease was 
of a very violent type, and would assuredly have proved fatal if left to run its course. 
The freezing had certainly failed to impair the virulence; it had rather sealed it up to 
be opened and given free course on the occurrence of a thaw; for, once it is frozen, 
it is manifest that no further change could take place until it was again thawed out, 
and if it was preserved for one nigbt unchanged in its potency, it would be equally 
unafiected after the lapse of many months, provided its liquids had remained in the 
same crystalline condition throughout. In this way undoubtedly the virus is often 
preserved through the winter in pens and yards, as well as in cars and other convey- 
ances, to break forth anew with returning spring. This is precisely what we find to 
be the case with the other fatal animal plagues, the virus of rinderpest, lung fever, 
anthrax, and aphthous fever, being often bound up through the winter with frozen 
manure to reappear with undiminished power on the accessof warmer weather. This 
is a matter of no small moment inasmuch as the long-continued frosts of our Northern 
States prevent any such destruction of the poison as takes place so readily in summer 
in connection with the alternate wetting and drying and the resulting putrefaction. 
I have had instances brought under my notice in which, after the prevalence of the 
fever in a herd in early summer, new swine were introduced into the open yard a 
month or two after all trace of the disease had disappeared and had continued to pre- 
serve the most perfect health. This is quite in keeping, too, with my failure in the 
attempts to convey the disease by feeding and inoculating with a semi-putrid intestine. 
It serves, moreover, to explain my failure, as the exposure and wet at a moderately 
high temperature would lead in both cases alike to decomposition and destruction. 
The bearing of this upon the prevention of the disease isself-evident. Infected yards 
and other open and uncovered places may be considered safe after two months’ vaca- 
tion in summer, provided that sufficient rain has fallen in the interval to insure the 
soaking and putrid decomposition of all organic matter near the surface, and that 
there are no great accumulations of manure, straw, hay, or other material in which 
the virus may be preserved dry and infecting. In winter, on the other hand, the yard 
or other open infected place may prove non-infecting for weeks and months, and yet 
retain the virus in readiness for a new and deadly career as soon as a thaw sets in. 
Safety in such circumstances is contingent on a disuse of the premises so long as the 
frost continues and for at least one month thereafter. Even during the continuance 
| of frost such places are dangerous, as the heat of the animals’ bodies or of the rays of 
