G. P. No. 4567. Six c. c. antitoxic horse serum (Natl. VIII. 18) injected into the peritoneal 
cavity. No symptoms. 
[Previous treatment: 65 days prior, as g. p. 4534.] 
G. P. No. 4554. Do. 
G. P. No. 4553. Do. 
DIPHTHERIA ANTITOXIN PLAYS NO ROLE IN THIS ACTION. 
Before we realized that the diphtheria toxine or antitoxin played 
no role in rendering guinea pigs susceptible to subsequent injections 
of horse serum we prepared the following series of guinea pigs, in 
order to eliminate the antitoxin as a factor. These pigs were injected 
subcutaneously with a mixture of 1 c. c. of normal horse serum and 
a small quantity of diphtheria toxine, slightly less than a minimal 
lethal dose. This was done for comparison with the susceptibility 
produced by the toxine-antitoxin mixtures. 
G. P. No. 91. Six c. c. normal horse serum (roan) injected into the peritoneal cavity. 
Symptoms. Died 12 hours later. 
[Previous treatment: 65 days prior, inoculated subcutaneously with 0.002 c. c. toxine 
No. 7+1 c. c. normal horse serum (Sam).] 
G. P. No. 296. Six c. c. normal horse serum (roan) injected into the peritoneal cavity. 
Dead in 60 minutes. 
[Previous treatment: 71 days prior, inoculated subcutaneously with 0.002 c. c. toxine 
No. 7+1 c. c. normal horse serum (Sam).] 
G. P. No. 66. Do. Dead in 40 minutes. 
G. P. No. 93. Do. Symptoms; recovered. 
G. P. No. 60. Do. 
It will be seen from our experiments that guinea pigs are quite as 
sensitive when previously treated with toxine-normal serum as with 
the toxine-antitoxin mixtures. 
In order to compare the toxic action of normal serum with anti- 
toxic serum upon pigs so treated, four animals of the above series 
were inoculated with antitoxic horse serum, as follows : 
G. P. No. 92. Six c. c. antitoxic horse serum (Natl. VIII. 17) injected into the peritoneal 
cavity. Symptoms. Died 12 hours later. 
[Previous treatment: 15 days prior, inoculated subcutaneously with 0.002 c. c. toxine 
No. 7+1 c. c. normal horse serum (Sam).] 
G. P. No. 98. Six c. c. antitoxic horse serum (Natl. VIII. 18) injected into the peritoneal 
cavity. Dead in 53 minutes. 
[Previous treatment: 58 days prior, inoculated subcutaneously with 0.002 c. c. toxine 
No. 7+1 c. c. normal horse serum (Sam).] 
G. P. No. 95. Do. Dead in 43 minutes. 
G. P. No. 94. Same injection. Symptoms; recovered. 
[Previous treatment: 65 days prior, inoculated subcutaneously with 0.002 c. c. toxine 
No. 7+1 c. c. normal horse serum (Sam).] 
It is evident from the above that fresh normal serum is quite as 
poisonous to a sensitized guinea pig as is antitoxic horse serum. 
