43 
The following guinea pigs were inoculated with horse serum eight 
and one-half years old: 
G. P. No. 258. Six c. c. antiamarillic serum injected into the peritoneal cavity. Dead in 
40 min. 
[Previous treatment: 24 days prior, inoculated subcutaneously with c. c. normal 
horse serum (roan) heated to 60° C. for two hours.] 
G. P. No. 256. Same injection. Symptoms, recovered. 
[Previous treatment: 20 days prior, inoculated subcutaneously with c. c. normal 
horse serum (roan) heated to 60° C. for two hours.] 
From the above experiments we see that blood serum over eight 
and one-half years old is as poisonous to sensitized pigs as fresh 
serum. 
EFFECT OF X-RAYS UPON THE TOXIC PRINCIPLE. 
Normal horse serum (roan) was exposed to the action of X rays, 
40 amperes, 4 inches from the tube for forty minutes, then injected 
into a susceptible guinea pig. It was found as poisonous as horse 
serum not so treated. 
G. P. No. 6A. Six c.c. above serum injected into peritoneal cavity. Dead in 10 minutes. 
[Previous treatment: 33 days prior, inoculated subcutaneously with 0.293 c, c. toxine 
No. 7+1 unit antitoxic horse serum (Standard B28).] 
