Part VTL 
SENSITIZING SUBSTANCE. 
We already know that guinea pigs may be sensitized with either 
normal or antitoxic horse serum. It is of course both interesting 
and important to know whether the substance contained in horse 
serum which renders the guinea pigs sensitive is the same as the sub- 
stance which exerts its poisonous action upon the second injection. 
GUINEA PIGS MAY BE SENSITIZED WITH PRECIPITATED AND DIALYZED SERUM. 
V 
The following examples selected from our work demonstrate this 
point: 
G. P. No. 4972. One c. c. normal horse serum (roan) injected into the peritoneal cavity. 
Symptoms; recoyered. 
[Previous treatment: 22 days prior, inoculated subcutaneously with 0.139 c. c. toxine 
Xo. o+g-g-Q c. c. antitoxic horse serum (XYBH 13C, precipitated and dialyzed in accord- 
ance with Gibson’s method).] 
G. P. Xo. 4973. Do. 
G. P. Xo. 4955. Six c. c. same serum.. Dead in 27 minutes. 
[Previous treatment: 40 days prior, inoculated subcutaneously with 0.139 c. c. toxine 
Xo. 5+^4^ c. c. antitoxic horse serum (XYBH 10B).] 
G. P. Xo. 4957. Same injection. Symptoms; recovered. 
[Previous treatment: 40 days prior, inoculated subcutaneously with 0.139 c. c. toxine 
Xo.. c. c. antitoxic horse serum (XYBH 10B).] 
DRYING DOES NOT INJURE THE SENSITIZING SUBSTANCE. 
A number of guinea pigs which were used by us in this work were 
sensitized with the antitoxic serum preserved under special condi- 
tions in this laboratory as the official standard in accordance with the 
law of July 1, 1902. This serum was reduced to dryness under special 
conditions and must be redissolved before using. Compare page 39. 
The following are selected as experimental data proving that dry- 
ing does not injure the sensitizing substance: 
G. P. Xo. 6B. Six c. c. antitoxic horse serum (Xatl. YIII. 17) injected into the peritoneal 
cavity. Dead in 27 minutes. 
[Previous treatment: 86 days prior inoculated subcutaneously with 0.22 c. c. toxine 
Xo. 7+1 unit antitoxic horse serum (Standard B25).] 
G. P. Xo. 4488. Same injection. Dead in 10 minutes. 
[Previous treatment : 12 days prior, inoculated subcutaneously with 0.19 c. c. toxine 
Xo. 7+1 unit antitoxic horse serum (Standard B27).] 
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