SOME REMARKS ON ANTI-HOG CHOLERA SERUM. 
675- 
and so on, until a passage tlirough ii animals had been reaelied j 
the amount injeeted into the last 4 animals was gradually di¬ 
minished, so that rabbit No. ii reeeived only .10 c. c. The 
animals were as near as possible all of the same size and breed, 
and all of them were males ; they weighed from 1600 to 2200 
grammes. 
In the eourse of this series the time elapsing between injec¬ 
tion and death grew shorter and shorter, so that the last rabbit 
died 48 hours after inoculaticu. From the spleen of this rabbit 
pure cultures were obtained, and ^ agar 
culure of this material proved now to be sufficient to kill, when 
subcutaneously administered, a medium-sized rabbit within 48 
hours. The same amount was needed to kill a 400-gramme 
guinea-pig in about the same time. The lesions produced in both 
kinds of animals were those typical to this infection, and which 
have been described by many authors. I must mention, how¬ 
ever, that while the less virulent races produced an abscess at the 
site of the injection, I never observed any local reaction with 
the more virulent ones. By an occasional passage through a 
rabbit it was easy to maintain this degree of virulence. 
I have no doubt that it would have been an easy task to, in 
the way described, increase the virulence beyond the point 
reached by me ; from what Voges says, I must infer that he has 
arrived at higher degrees. But I concluded not to exaggerate 
this rabbit—or guinea-pig—virulence, because it was easily pos¬ 
sible that it was only one-sided, and had no bearing on the be¬ 
havior of the bacilli towards hogs. 
When smaller doses than .5 mg. were injected, the animals 
mostly recovered after a protracted illness. The blood serum of 
such animals had a very decided agglutinating power on the 
bacilli, a phenomenon that has already been described by 
Cashin * and others. In some cases this power was apparent 
at a dilution of i to 120. I mention this fact here because from 
it the conclusion has been drawn, that like in typhoid fever no 
antitoxic substances were formed in the blood of animals recov 
* New York Medical Journal, 1897. 
