29 
guinea pigs treated with the serum of other animals (dog, hog, rat, 
cattle, sheep, cat) become as highly sensitized to a second injection 
of the homologous serum. 
The following series of guinea pigs were all sensitized with 1 /250 
c. c. of the blood of various animals. Subsequently they were injected 
with horse serum to which they either did not respond or, after 
characteristic symptoms, recovered. These guinea pigs were finally 
injected with large quantities of the same kind of serum as that used 
at the first injection. 
Dog serum. 
G. P. Xo. 214. Six c. c. antitoxic horse serum (Xatl. IX. 17) injected into the peritoneal 
cavity. Xo symptoms. 
[Previous treatment: 26 days prior, inoculated subcutaneously with jto c - c - dog 
serum.] 
5 hrs. later 6 c. c. dog serum injected into the peritoneal cavity. Symptoms. 
G. P. Xo. 215. Six c. c. antitoxic horse serum (Xatl. IX. 17) injected into the peritoneal 
cavity. Xo symptoms. 
[Previous treatment: 35 days prior, inoculated subcutaneously with ^fo c - c - dog 
serum.] 
22 days later 6 c. c. dog serum injected into peritoneal cavity. Severe symptoms. 
G. P. Xo. 212. Six c. c. antitoxic horse serum (Xatl. IX. 17) injected into the peritoneal 
cavity. Mild symptoms. 
[Previous treatment: 35 days prior, inoculated subcutaneously with ^fo c - c - dog 
serum.] 
22 days later 6 c. c. dog serum injected into peritoneal cavity. Severe symptoms. 
G. P. Xo. 211. Four c. c. normal horse serum (roan) injected into the peritoneal cavity. 
Symptoms. 
[Previous treatment: 56 days prior, inoculated subcutaneously with ^to c - c - dog 
serum.] 
1 day later 6 c. c. dog serum injected into the peritoneal cavity. Dead in 35 minutes 
Hog serum. 
G. P. Xo. 186. Six c. c. antitoxic horse serum (Xatl. EX. 17) injected into the peritoneal 
cavity. Severe symptoms. 
[Previous treatment: 30 days prior, inoculated subcutaneously with 2 x 0 c. c. hog 
serum.] 
22 days later 6 c. c. hog serum injected into the peritoneal cavity. Severe symptoms. 
G. P. Xo. 185. Six c. c. antitoxic horse serum (Natl. IX. 17) injected into the peritoneal 
cavity. Xo symptoms. 
[Previous treatment: 30 days prior, inoculated subcutaneously with ^Eg- c. c. hog 
serum.] 
22 days later 5 c. c. hog serum injected into the peritoneal cavity. Xo symptoms. 
G. P. Xo. 187. Four c. c. antitoxic horse serum (Xatl. IX. 17) injected into the peritoneal 
cavity. Xo symptoms. 
[Previous treatment: 51 days prior, inoculated subcutaneously with 2 x 0 c. c. hog 
serum.] 
1 day later 6 c. c. hog serum injected into the peritoneal cavity. Symptoms. 
G. P. Xo. 189. Same injection and previous treatment. Xo symptoms. 
1 day later 6 c. c. hog serum injected into the peritoneal cavity. Symptoms. 
