38 
blood of man following the injection is variable. It sometimes 
disappears in the fourth week, and sometimes is still markedly 
present in the ninth week. 
Finally, we know that the precipitins are strictly specific, whereas 
the toxic action is only quantitatively specific. 
EFFECT OF HEAT UPON THE TOXICITY OF HORSE SERUM. 
One of the first questions which required solution was whether 
the toxic substance in blood serum is thermolabile. That it is able 
to withstand a comparatively high degree of heat for a long time, 
viz, 60° C. for six hours, is evident from the following experiments: 
G. P. No. 4349. Six c. c. antitoxic horse serum (Natl. VIII. 17) heated to 60° C. for 30 
minutes, then injected into the peritoneal cavity. Dead in 30 minutes. 
G. P. No. 60. One c. c. same serum and injection as g. p. 4349. Dead in 10 minutes. 
[Previous treatment: With toxine-antitoxin mixture.] 
G. P. No. 61. Do. Dead in 10 minutes. 
G. P. No. 62. Do. Symptoms; recovered. 
G. P. No. 4897. Injected with 5 c. c. of an extract of normal horse serum (roan) heated to 
60° C. for 6 hours. This degree of heat coagulated the serum. About 1 c. c. of the coagu- 
lum was added to 9 c. c. of salt solution, thoroughly shaken up, filtered, and the filtrate 
injected into the peritoneal cavity. Symptoms; death in about 3 hours. 
[Previous treatment: 41 days prior, injected subcutaneously with 0.139 c. c. toxine 
No. 5+- g-g-g- c. c. horse serum (Alex. No. 192).] 
G. P. No. 4508. Six c. c.of an extract of antitoxic horse serum (Natl. IX. 19) heated to 
100° C. for 15 minutes, injected into the peritoneal cavity. The coagulum was ground up 
with a few c. c. of salt solution and strained through gauze before being injected. No 
symptoms. 
One and a half hours later about 8 c. c. of the coagulum was ground up and the entire 
mass, not strained, injected into the peritoneal cavity of the same guinea pig. No 
symptoms. 
G. P. No. 5048. Six c. c.of the coagulum of normal horse serum (roan) heated to 100° C. 
for 15 minutes and ground up with salt solution (0.85) injected into the peritoneal cavity. 
No symptoms. 
[Previous treatment: 20 days prior, inoculated subcutaneously with 0.22 c. c. toxine 
No. 7+-^ 7 c. c. antitoxic horse serum (Alex. A204).] 
From the above it is evident that while a temperature of 60° C. 
continued for six hours has practically no influence upon the toxic 
substance in horse serum, the toxicity is entirely destroyed by a 
temperature of 100° C. for fifteen minutes. 
THE TOXIC PRINCIPLE IN HORSE SERUM IS FILTERABLE THROUGH PORCELAIN. 
The following experiment is sufficient to demonstrate that the 
close-grained pores of a Pasteur-Chamberland filter B do not retain 
the toxic principle of horse serum: 
G. P. No. 4521. Six c. c. of antitoxic horse serum (Natl. VIII. 17) filtered through a Pas- 
teur-Chamberland filter B and injected into the peritoneal cavity. Dead in 35 minutes. 
[Previous treatment: 32 days prior, inoculated subcutaneously with 0.19 c. c. toxine 
No. 7—1 unit horse serum (Standard B27).] 
