370 STUDIES IN IMMUNITY. 



escaped the attention of these writers. Heated bovine serum hus 

 only a slight agglutinating property for guinea-pig corpuscles. 

 Fresh horse serum does agglutinate them, but only slowly and when 

 present in relatively large amounts, several hours may be required 

 to clump the corpuscles in any considerable masses. A mixture of 

 the two sera, however, agglutinates in a very few minutes, and the 

 corpuscles soon form veritable chunks that stick to the glass. We 

 may mention in this connection an experiment with fresh horse 

 serum (alexin), bovine serum heated to 56 degrees, and a 5 per 

 cent suspension of washed guinea-pig corpuscles; mixtures are 

 prepared as follows: 



1. Corpuscle suspension, 1 c.c.; bovine serum, 56 degrees, 0.5 

 of a cubic centimeter. 



2. Corpuscles, 1 c.c.; horse serum, 0.5 of a cubic centimeter. 



3. Corpuscles, 1 c.c.; 0.5 of a cubic centimeter of a mixture in 

 equal parts of the two sera. 



There is intense agglutination in 3 in a few minutes; hemolysis 

 begins shortly after and later becomes complete; mixtures 1 and 2 

 not only are not hemolyzed, but show only a very delayed agglu- 

 tination which is never comparable with the one in 3. 



A slight variation in the experiment may be made by nrnking 

 mixtures 1 and 2 and then mixing them. The corpuscles rapidly 

 agglutinate in a mixture of the two sera and are soon laked.* It 

 should be noted at once that if horse serum heated to 56 degrees 

 is added in place of fresh horse serum to the heated bovine serum 

 there is not only no hemolysis, but also none of this intense agglu- 

 tination. The agglutination, then, would seem in some way depend- 

 ent on the presence of active alexin. 



This is a rather curious condition. If an explanation were sought 

 according to Ehrlich and Sachs' explanation, we should have to 

 conclude that the agglutinin as well as the sensitizer must combine 

 with the alexin before uniting with the corpuscle. Such a con- 

 clusion is unusual, for there are no facts that would lead us to assume 

 that the agglutinins need alexins to be efficient. 



Ehrlich and Sachs' theory of the mode of action of these two sera 

 seems already open to criticism. We must therefore consider in 



* This agglutination takes place at room temperature, but is more rapid at 

 37 degrees. 



