36 
Normal G. P. No. 1. Killed the same day with chloroform, blood defibrinated, and the 
serum separated in the centrifuge. 
Normal G. P. No. 2. Killed by chloroform 3 days previously and the serum allowed to sepa- 
rate by coagulation. 
(Two tests made of each serum.) 
• 
1 c. c. horse serum (1:21). 
0.1 c. c. serum 
normal guinea 
Pig 1- 
0.1 c. c. serum 
normal guinea 
pig 2. 
Normal horse serum (Sam) 
Nil. 
Nil. 
Nil. 
Nil. 
Normal horse serum (Jane) 
Nil. 
Nil. 
Nil. 
Nil. 
Antitoxic horse serum (Natl. VIII, 17) 
Nil. 
Nil. 
Nil. 
Nil. 
Antitoxic horse serum fHubbert op. 1) 
Nil. 
Nil. 
Slight precipi- 
tation^). 
Nil. 
Antitoxic horse serum (Natl. IX, 17) 
Nil. 
Nil. 
Nil. 
Nil. 
Antitoxic horse serum (Stearns 1110) 
Nil. 
Nil. 
Nil. 
Nil. 
From this and other similar experiments we are justified in conclud- 
ing that neither normal horse serum nor antitoxic horse serum has any 
power to precipitate normal guinea-pig serum. 
We next made some tests to determine whether a guinea pig pre- 
viously treated with one small injection of horse serum developed 
precipitins. 
One c. c. of horse serum both normal and antitoxic in dilution of 
1 : 21 was placed in small tubes, as before, and 0.1 c. c. of a sensitized 
guinea-pig serum added to each tube, as shown in the table. They 
were shaken and placed in the incubator and results read after 
twenty-four hours. 
G. P. No. 4617. [Preyious treatment: 35 days prior, inoculated subcutaneously with 0.19 
c. c. toxine No. 7-j-l unit horse serum (standard B27).] 
G. P. No. 4510. [Previous treatment: same.] 
• 
1 c.c. horse serum (1:21). 
0.1 c.c. normal 
guinea-pig serum. 
0.1 c. c. treated 
guinea-pig serum. 
Centrif- 
ugation. 
Coagula- 
tion. 
Guinea 
pig 4517. 
Guinea 
pig 4510. 
Normal horse serum (Sam) 
0 
0 
0 
0 
Normal horse serum (Jane) 
0 
0 
0 
0 
Normal horse serum (S. P.) 
0 
0 
0 
0 
Normal donkev serum 
0 
0 
0 
0 
Antitoxic horse serum (Natl. VIII, 17) 
0 
0 
0 
0 
Antitoxic horse serum (Natl. V,14) 
0 
0 
0 
0 
Antitoxic horse serum (Natl. IX. 17) 
+(?) 
0 
0 
0 
Antitoxic horse serum (Stearns 1110) 
0 
0 
0 
0 
Antitoxic horse serum (Stearns 1429) 
0 
0 
0 
0 
It would therefore appear that guinea pigs which have previously 
been inoculated with one injection of a very small amount of horse 
serum sufficient to render them highly susceptible to a second injec- * 
tion of horse serum do not contain sufficient precipitin in their 
