HEMOLYTIC SERA AND THEIR ANTITOXINS. 205 



It was first determined that two parts of antitoxin (56 degrees) will neutralize 

 one part of alexin (fresh normal guinea-pig serum) . Two mixtures were prepared 

 as follows: 



a. Antitoxin, 2 c.c; fresh normal guinea-pig serum, 1 c.c. 



b. Antitoxin, 2 c.c; normal guinea-pig serum heated to 55 degrees, 1 c.c. 

 As a control the following mixtures were prepared: 



c. Antitoxin, 2 c.c; salt solution, 1 c.c. In this mixture the antitoxin is 

 simply diluted. 



d. Normal rabbit serum (55 degrees), 2 c.c; salt solution, 1 c.c. 



These four mixtures are then heated for half an hour to from 55 to 56 degrees. 

 The mixtures are subjected to exactly similar conditions, but mixture a, con- 

 taining fresh alexin, is naturally the one most affected, as the alexin is destroyed 

 at this temperature. 



After heating, the antitoxic value of the four mixtures is determined. For this 

 purpose a suitable dose of fresh normal guinea-pig serum is added to each tube.* 



Later well-sensitized rabbit blood is added to each tube. The amount of sensi- 

 tizer used is sufficiently large to prevent the antisensitizing effect of the antitoxin 

 from being noticeable. 



It is evident that the blood will hemolyze in mixtures in which the toxin (alexin) 

 has not been neutralized; in other words, in mixtures that do not contain active 

 anti-alexin. Hemolysis takes place quickly in d, which contains no antitoxin. 

 Corpuscles remain intact in c, containing a mixture of antitoxin and salt solu- 

 tion. Mixtures a and b do not act exactly alike. In b the corpuscles remain 

 intact, as in c, for a long time, but finally become partially hemolyzed; in mixture 

 a hemolysis is very energetic. The contrast between a and 6 is very striking. 

 In a there is only a slight antitoxic effect: unheated normal serum neutralizes 

 antitoxin much more distinctly than does heated serum. 



We shall not consider farther for the present the mechanism by 

 which the antitoxic serum protects corpuscles from the hemotoxin, 

 but shall hope to return later to a consideration of this question. 

 We may mention in conclusion that the antitoxin has also anti- 

 agglutinating properties against the hemolytic serum. It also 

 causes a precipitate both with hemolytic serum and also with normal 

 guinea-pig serum. This precipitating property exists, not only in 

 animals that furnish antitoxin (i.e., rabbits treated with hemolytic 

 serum), but also in rabbits given injections of defibrinated blood or 

 normal guinea-pig serum. We refer to our previous article for more 

 information on this property of serum. f 



* The amount of normal serum that is best to add is determined by using a 

 series of tubes corresponding to each mixture a, b, etc., to each one of which a 

 different amount of alexin is added. 



f We may recall simply that the "precipitating property" of such a serum is 

 quite distinct from its antitoxic property. Nor has it any relation to the agglu- 

 tinating property of the serum for corpuscles. 



