52 
SMALL QUANTITIES OF HORSE SERUM MAY RENDER GUINEA PIGS MORE SUSCEP- 
TIBLE THAN LARGE QUANTITIES. 
Before we learned that the antitoxin contained in the blood serum 
of the horse plays no role in rendering guinea pigs susceptible to 
subsequent inoculations of horse serum we planned and carried out 
an extensive series of experiments to determine just what relation 
the susceptibility of guinea pigs bears to the antitoxic potency of 
the horse serum injected. One series of guinea pigs was injected 
subcutaneously with one unit of an antitoxic horse serum containing 
250 units to the c. c. This series, therefore, received c. c. of horse 
serum. The second series was treated subcutaneously with 250 
units— that is, the guinea pigs received 1 c. c. of the horse serum. 
The third series of guinea pigs was treated with 1,000 units — that is, 
each guinea pig received 4 c. c. of the antitoxic horse serum. At 
varying intervals following these injections the pigs were given a 
second injection of horse serum in order to determine their sus- 
ceptibility. 
The following guinea pigs received c. c. antitoxic horse serum 
containing 1 unit: 
G. P. No. 18. Six c. c. antitoxic horse serum (Natl. VIII. 17) injected into the peritoneal 
cavity. 
[Previous treatment: 1 day prior, inoculated subcutaneously with 1 unit, viz, ^ro c - c -> 
horse serum (Natl. IX. 18).] No symptoms. 
G. P. No. 17. Same injection as g. p. 18. No symptoms. 
[Previous treatment: 4 days prior, as g. p. 18-1 
G. P. No. 11. Same injection as g. p. 18. Dead in 35 minutes. 
[Previous treatment: 17 days prior, as g. p. 18.] 
G. P. No. 16. Same injection as g. p. 18. Symptoms; recovered. 
[Previous treatment: 18 days prior, as g. p. 18.] 
G. P. No. 15. Same injection as g. p. 18. Dead in 18 minutes. 
[Previous treatment: 24 days prior, as g. p. 18.] 
G. P. No. 19. Same injection as g. p. 18. Symptoms; recovered. 
[Previous treatment: 32 days prior, as g. p. 18.] 
G. P. No. 12. Six c. c. antitoxic horse serum (Natl. IX. 17) injected into peritoneal cavity. 
Dead in 44 minutes. 
[Previous treatment: 47 days prior, as g. p. 18.] 
G. P. No. 10. Six c. c. antitoxic horse serum (Natl. IX. 19) injected into the pertioneal 
cavity. No symptoms. 
[Previous treatment: 47 days prior, as g. p. 18.] 
G. P. No. 13. Six c. c. antitoxic horse serum (Natl. VIII. 18) injected into the peritoneal 
cavity. Symptoms; recovered. 
[Previous treatment: 68 days prior, as g. p. 18.] 
The following guinea pigs received 1 c. c. antitoxic horse serum 
containing 250 units: 
G. P. No. 29. Six c. c. antitoxic horse serum (Natl. VIII. 17) injected into the peritoneal 
cavity. No symptoms. 
[Previous treatment: 1 day prior, inoculated subcutaneously with 250 units, viz, 1 c. c., 
horse serum (Natl. IX. 18).] 
