18 
The following mixture of toxine and antitoxin represents these two 
substances in the proportion of the L° dose: 
G. P. 4483. 1.6 c. c. toxine No. 7+11.5 units antitoxic serum (standard B27) injected sub- 
cutaneously. No symptoms. 
18 days later 6 c. c. antitoxic horse serum (National VIII, 17) injected into tbe peri- 
toneal cavity of the same pig. Death 30 minutes. 
In a similar way the effects of mixing large doses of the diphtheria 
toxine with normal horse serum were tested, as follows: 
G. P. No. 40. Six c. c. normal horse serum (roan horse)+ 0.3 c. c. diphtheria toxine No. 5 
mixed in vitro and injected into the peritoneal cavity. No immediate symptoms. Died 
2 days later. 
GUINEA PIGS CAN NOT BE RENDERED SUSCEPTIBLE BY PRIOR INFECTIONS WITH 
THE BACILLUS DIPHTHERIAL 
When this work was first undertaken it was thought to have a bear- 
ing upon sudden deaths in children suffering with diphtheria. The 
work was begun in order to discover, if possible, the cause of this acci- 
dent. We thought that possibly by injecting small quantities of a 
virulent culture of the Klebs-Loffler bacillus into guinea pigs, in that 
way imitating mild cases of diphtheria, some of these pigs could be 
rendered susceptible to subsequent inoculations of antitoxic horse 
serum. This, however, is not the case for guinea pigs, as is plainly 
seen in the following experiments, in which a number of guinea pigs 
were treated with sufficient quantities of a culture of the Klebs- 
Loffler bacillus to cause slight symptoms and at varying intervals of 
time were inoculated again into the peritoneal cavity with large 
quantities of antitoxic horse serum. In no instance did the guinea 
pigs show any ill effects from this latter treatment. 
G. P. No. 41. Six c. c. antitoxic horse serum (Natl. VIII, 17) injected into the peritoneal 
cavity. No symptoms. 
[Previous treatment: 4 days prior, inoculated subcutaneously with 0.1 c. c. suspension.] 
G. P. No 9. Six c. c. same serum and injection as g. p. 41. No symptoms. 
[Previous treatment: 7 days prior, inoculated subcutaneously with 1 gtt. of 24-hour 
suspension.] 
G. P. No. 51. Six c. c. same serum and injection as g. p. 41. No symptoms. 
[Previous treatment : 7 days prior, inoculated subcutaneously with 0.1 c. c. of suspen- 
sion. 
G. P. No. 42. Six c. c. same serum and injection as g. p. 41. No sjmiptoms. 
[Previous treatment: 9 days prior, inoculated subcutaneously with 1 gtt. 24-hour 
suspension.] 
G. P. No. 56. Six c. c. same serum and injection as g. p. 41. No symptoms. 
[Previous treatment : 9 days prior, inoculated subcutaneously with 0.1 c. c. suspension.] 
G. P. No. 43. Six c. c. same serum and injection as g. p. 41. No symptoms. 
[Previous treatment: 12 days prior, inoculated subcutaneously with 1 gtt. 24-hour 
suspension.] 
G. P. No. 45. Six c. c. same serum and injection as g. p. 41. No symptoms. 
[Previous treatment: 14 days prior, inoculated subcutaneously with 1 gtt. 24-hour 
suspension.] 
