Part VL 
DOSAGE AS A FACTOR. 
MINIMAL AMOUNT OF HORSE SERUM NECESSARY TO RENDER A GUINEA PIG 
SUSCEPTIBLE. 
A large part of our work was done upon guinea pigs which had 
been used to measure the strength of antitoxic serums. As the 
strength of diphtheria antitoxin runs between 250 and 1,000 units 
to the c. c. most of our guinea pigs were therefore rendered sus- 
ceptible by doses of horse serum varying from to T oVo c. c - If 
now becomes interesting to know how small a quantity of horse 
serum injected into a healthy guinea pig would render it susceptible 
to the toxic action of horse serum. 
G. P. No. 217. Six c. c. normal horse serum (roan) injected into the peritoneal cavity. 
Symptoms; recovered. 
[Previous treatment: 45 days prior, inoculated subcutaneously with x ^ c. c. antitoxic 
horse serum (Natl. IX. 19).] 
G. P. No. 219. Do. 
G. P. No. 216. Six c. c. antitoxic horse serum (Natl. IX. 17) injected into the peritoneal 
cavity. Symptoms; recovered. 
[Previous treatment: 24 days prior, inoculated subcutaneously with x ^ x c. c. antitoxic 
horse serum (Natl. IX. 19).] 
G. P. No. 222. Six c. c. antitoxic horse serum (Natl. IX. 17) injected into the peritoneal 
cavity. Symptoms; recovered. 
[Previous treatment: 24 days prior, inoculated subcutaneously with c - c - anti- 
toxic horse serum (Natl. IX. 19).] 
G. P. No. 223. Six c. c. normal horse serum (roan) injected into the peritoneal cavity. 
Dead in 130 minutes. 
[Previous treatment: 45 days prior, inoculated subcutaneously with tUtsis c - c - anti- 
toxic horse serum (Natl. IX. 19).] 
G. P. No. 220. Do. Dead in 68 minutes. 
G. P. No. 225. Six c. c. antitoxic horse serum (Natl. IX. 17) injected into the peritoneal 
cavity. Symptoms; recovered. 
[Previous treatment: 24 days prior, inoculated subcutaneously with c - c - antitoxic 
horse serum (Natl. IX. 19).] 
G. P. No. 224. Six c. c. normal horse serum (roan) injected into the peritoneal cavity. 
Symptoms; recovered. 
[Previous treatment: 45 days prior, inoculated subcutaneously with c - c * anti- 
toxic horse serum (Natl. IX. 19).] 
G. P. No. 227. Do. 
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