HOG CHOLERA. 
17 
admit the parasite. The theory taught by one of the early investi¬ 
gators of this malady, that a few germs wafted by the air might 
settle upon a slight abrasion of the skin and thus gain entrance to 
the body and produce fatal effects, is scarcely tenable in the light 
of recent experiments. We have found that hogs may be safely 
given from one-fourth to one-half of a cubic centimetre of virulent 
cultures by hypodermic injection. Each drop of such cultures con¬ 
tains about two millions of microbes, and hence from twelve to twen¬ 
ty-five millions of these germs may be placed beneath the skin with¬ 
out danger to the hog. By the side of these vast numbers, of what 
significance is the half dozen germs which according to this gen¬ 
tleman are borne by the breeze and dropped upon an abraded 
surface of the skin? I must confess that I am skeptical of the 
disease ever being produced in this manner. 
I shall not go into the details of preventive measures in this 
paper. You are already familiar with the principles of sanitary 
science which are applicable to diseases of this class. What you 
are doubtless interested in is the new points which may have been 
brought out by our investigations. 
The most interesting of these is our attempt to confer immu¬ 
nity by inoculation. We soon found that there was no indication 
for attenuating the virus for this purpose, because the strongest 
virus might be introduced hypodermically with impunity in con¬ 
siderable doses. Now as the stronger a virus is the higher degree, 
of immunity it produces, you can see that there is every reason 
for using the fresh unattenuated cultures. But even these are not 
sufficient. We made many experiments and found that hogs 
might safely be inoculated with one-fourth to one-half cc. for the 
first dose and that the second dose might safely be increased to 
* 
two and three cc. showing that some degree of immunity had 
been gained. These twice-inoculated animals, however, were still 
unable to withstand exposure in an infected pen, and could not be 
fed the virus without fatal results. 
We have tested many disinfectants and have determined the 
exact strength in which they should be used and the period of 
time necessary to kill the germ. The most useful agent for dis¬ 
infecting manure and soil is undoubtedly lime. This in the pro¬ 
portion of one-fourth to one-half of one per cent, is speedily fatal 
