382 STUDIES IN IMMUNITY. 



is added, the corpuscles would show neither hemolysis nor aggluti- 

 nation. Experimentally we find this to be true. Bovine blood is 

 sensitized with three volumes of serum from an immunized rabbit. 

 The corpuscles are then washed, the original volume of the blood 

 reestablished and an equal amount of fresh horse serum added. 

 After a time this mixture is centrifugalized and the supernatant 

 fluid is employed as horse serum deprived of alexin. As a control 

 we use horse serum that has been treated in exactly the same man- 

 ner with unsensitized bovine corpuscles. The following mixtures 

 are then prepared: 



(a) 5 per cent suspension of guinea-pig corpuscles, 1 c.c. ; bovine 

 serum (56 degrees), 0.3 c.c.; treated horse serum, 0.6 c.c. 



(b) Corpuscle suspension, 1 c.c.; bovine serum (56 degrees), 

 0.3 c.c.; control horse serum, 0.6 c.c. 



(c) Corpuscle suspension, 1 c.c.; bovine serum (56 degrees), 

 0.3 c.c.; a mixture of equal parts of salt solution and fresh horse 

 serum, 0.6 c.c. 



As a result, agglutination appears rapidly in "b" and "c," followed 

 by hemolysis. There is no agglutination or hemolysis in "a." 



The same experiment with sensitized ox corpuscles in place of 

 guinea-pig corpuscles gives a similar result. 



It is to be noted in passing that this experiment also furnishes a 

 proof of the functional unity of the alexin. Horse serum that has 

 been deprived of alexin for bovine corpuscles has likewise lost its 

 alexic activity for guinea-pig corpuscles. Both species of cor- 

 puscles, therefore, are sensitive to the same alexin. 



Fifth : According to our idea, in Ehrlich and Sachs' experiment the 

 fresh horse serum not only furnishes the alexin for the guinea-pig 

 corpuscles, but is also of prime importance in sensitizing them. 

 Guinea-pig corpuscles that have been placed in contact with fresh 

 horse serum alone, and then washed and so deprived of the excess 

 of serum, should be both sensitized and alexinized, in other words, 

 able to fix the colloidal substance; they should therefore be agglu- 

 tinated on the addition of heated bovine serum, whereas normal 

 guinea-pig corpuscles will show no such effect. We find this, experi- 

 mentally, to be true. As a control, it is shown that corpuscles treated 

 in the reverse manner, that is to say, by heated bovine serum first, 

 washed, and then horse serum, show no agglutination. 



