Part IX. 
IMMUNITY. 
ACTIVE IMMUNITY. 
GUINEA PIGS MAY BE IMMUNIZED AGAINST THE TOXIC SUBSTANCE IN 
HORSE SERUM. 
Guinea pigs may be immunized against this toxic substance, fol- 
lowing the lines of active immunity produced by repeated inocula- 
tions, of bacterial toxins. For instance, a guinea pig that has received 
an injection daily for ten days of small quantities (1 c. c.) of horse 
serum develops a high degree of immunity to subsequent injections 
of horse serum. Guinea pigs that have received more than ten inoc- 
ulations on ten successive days develop a still higher degree of 
immunitv. 
G. P. No. 109. Six c. c. antitoxic horse serum (Natl. IX. 19) injected into the peritoneal 
cavity. No symptoms. 
[Previous treatment: 15 to 27 days prior, 10 subcutaneous inoculations, 1 c. c. each, 
of antitoxic horse serum (Natl. IX. 19).] 
G. P. No. 111. Six c. c. antitoxic horse serum (Natl. VIII. 18) injected into the peritoneal 
cavity. No symptoms. 
[Previous treatment: 36 to 48 days prior, 10 subcutaneous inoculations, 1 c. c. each, 
normal horse serum (Sam).] 
G. P. No. 107. Six c. c. antitoxic horse serum (Natl. IX. 19) injected into the peritoneal 
cavity. Symptoms; recovered. 
[Previous treatment: 15 to 27 days prior, 10 subcutaneous inoculations, 1 c. c. each, 
normal horse serum (Sam).] 
G. P. No. 106. Six c. c. antitoxic horse serum (Natl. VIII. 18) injected into the peritoneal 
cavity. No symptoms. 
[Previous treatment: 36 to 48 days prior, 10 subcutaneous inoculations, 1 c. c. each, 
normal horse serum (Sam).] 
G. P. No. 108. Six c. c. antitoxic horse serum (Natl. VIII. 18) injected into the peritoneal 
cavity. Symptoms; recovered. 
[Prior treatment: 37 to 50 days prior, 10 subcutaneous inoculations, 1 c. c. each, 
normal horse serum (Sam).] 
6 days later, 1 c. c. normal horse serum (roan) inoculated subcutaneously on each of 12 
successive days. No symptoms. 
6 days later, 6 c. c. normal horse serum (roan) into peritoneal cavity. No symptoms. 
G. P. No. 110. Six c. c. antitoxic horse serum (Natl. VIII. 18) injected into the peritoneal 
cavity. Symptoms; recovered. 
[Previous treatment: 37 to 50 days prior, 10 subcutaneous inoculations, 1 c. c. each, 
antitoxic horse serum (Natl. IX. 19).] 
6 days later, 1 c. c. normal horse serum (roan) inoculated subcutaneously on each of 12 
successive days. No symptoms. 
6 days later, 6 c. c. normal horse serum (roan) into peritoneal cavity. No symptoms. 
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