DISEASES OF SWINE AND OTHER ANIMALS. 355 
of hogs and pigs that have been ringed. These morbid changes in the 
skin, it would seem, are produced in a similar way as the morbid growths 
in the intestines, with only this difference, that instead of an excrescence 
loss of substance makes its appearance. The skin is constantiy exposed 
to the atmospheric air, and to a much lower and more changeable tem- 
perature than the mucous membrane of the intestines, and in consequence 
the process of decay may become more rapid and may exceed the prob- 
ably slower process of production. 
/ 
7. PERIOD OF, INCUBATION. 
The period of incubation—perhaps more correctly ‘“‘stage of coloniza- 
tion,” Klebs—or the time passing between an infection and the first out- 
break of the disease, I have found to be from five to fifteen days, or on 
an average of about seven days. Still, [have no doubt that in single 
cases an outbreak may take place a day or two sooner, and in others, 
though rarely, a day or two later. 
8. MEASURES OF PREVENTION. 
As swine-plague is a contagious or infectious disease, which spreads 
everywhere by means of direct and indirect infection, and as a sponta- 
neous development is problematic, or has not yet been proven, the prin- 
cipal means of preventior must consist in preventing a dissemination of 
the contagious or infectious principle, and in an immediate, prompt, and 
thorough destruction of the same wherever it may be found. To prevent 
successfully a dissemination of the contagion and to secure a prompt 
destruction of the same, stringent legislation will be found necessary. 
As it is, the contagion or the infectious principle is, and has been, 
disseminated through the whole country in a wholesale manner, as I 
shall show immediately. During the first month of my presence in 
Champaign I stopped at the Doane House, a hotel belonging to the 
Iilinois Central Railroad Company, and constituting also the railroad 
depot. Every night car-loads of diseased hogs destined for Chicago 
passed my window. Only a very short time ago, on one of the last 
days of October, a farmer, J.T. M., living near Tolono, sold sixty-seven 
hogs (some, if not all of them, diseased and a few of them already in a 
dying condition) for two cents a pound, to be shipped to Chicago. I 
could cite numerous instances, but I think it is not necessary, because 
these facts are known to every one where swine-plague is prevailing. 
Besides, in nearly every little town in the neighborhood of which cases 
of swine-plague are of frequent occurrence, is a rendering establishment 
to which dead hogs are brought. These establishments pay one cent a 
pound, and the farmers haul their dead hogs, sometimes ten or fifteen 
miles, in open wagons, past farms, barns, and hog-lots, and disseminate 
thereby the germs of the disease through the whole country. The trans- 
portation of dead hogs by wagon, I admit, might be stopped by State 
laws, but the latter prove usually to be ineffective where railroad com- 
panies (inter-State and international traffic) are concerned. I include 
international traffic, because swine-plague is or has been prevailing in 
Europe. Besides that, there are other contagious diseases which spread 
exclusively by means of their contagion—I will mention only gianders, 
foot and mouth disease or aphthe, and plewro-pneumonia of cattle—and 
can be stamped out and be prevented from spreading only by efficient 
Congressional legislation. Pleuro-pneumonia particularly deserves spe- 
