28 
FRANK S. BILLINGS. 
capable of killing hogs in about five days, and have no doubt that 
it can be done as soon as we have means to experiment properly. 
This fact settled, we shall then have a simple and more practical 
way of obtaining material than by taking material from sick 
swine, where I find there is a great variation in the natural viru¬ 
lence of the germs. 
On account of having no place suitable to breed and keep 
small animals this winter, I have been really unnecessarily 
retarded in my work, as I think, had its value been truly appre¬ 
ciated, such room could have been supplied me. As it is, I can 
but think that the work done should satisfy every reasonable 
person of its quality, and my known skepticism should be a sure 
guarantee of the trustworthiness of the results. I am prepared 
to subject the above pigs to any test that may be suggested 
before a committee of farmers or members of the Legislature, had 
we means to do it. All we now need is the means to make one 
grand test experiment, which I propose to do as soon as the 
funds you have so kindly asked for are at our disposal. 
I shall then request a committee of the Board of Agriculture 
to watch the experiment, and shall inoculate one hundred pigs in 
different ways and with different amounts, and then place an 
equal number of diseased hogs among them, and some fifty 
healthy ones, and am confident that I shall be able to previously 
name the hogs that will withstand infection on such exposure. 
When these results are compared with those made with vac¬ 
cine inoculations to prevent anthrax, they seem to show that the 
time in which an artificial immunity can be produced in suscepti¬ 
ble animal organisms is dependent upon the virulence of the dis¬ 
ease in question; that is, that the time in which artificial immun¬ 
ity can be produced in any given disease will be found to depend 
upon the rapidity of the course of said disease under natural 
conditions. Take anthrax, for instance, a disease, the course of 
which can better be counted by hours than days. According to the 
reports which have come to us of the results with Pasteur’s vac¬ 
cine, and the methods used to inoculate show that even in that 
disease it takes from fifteen to twenty days to produce a reliable 
artificial immunity, but even then, in this case, there seems to be 
