446 STUDIES IN IMMUNITY. 



these substances they are then in a position to unite with the bovine 

 colloid, which clumps them and renders them more susceptible to 

 hemolysis. The second assertion of Bordet and Gay, to which we 

 have already referred, is that bovine serum presents no abnormality 

 so far as its amboceptor is concerned. This sensitizer is able to 

 unite with the corpuscles when the alexin is absent, contrary to the 

 opinion of Ehrlich and Sachs. Heated bovine serum that has been 

 subjected to a large amount of guinea-pig corpuscles still acts as if it 

 had lost no essential element because its colloid has been retained. 

 This is due to the fact that the corpuscles used to absorb the serum 

 were not alexinized and consequently could not combine with the 

 colloid. Such a treated serum, however, has lost its amboceptor. 

 But inasmuch as this lack may be replaced by the sensitizer in horse 

 serum, a mixture of bovine serum treated in this manner, of fresh 

 horse serum and of guinea-pig corpuscles, acts almost exactly as 

 when intact bovine serum is used. 



It is necessary to explain these matters rather in detail, inasmuch 

 as the mechanism in the experiment under consideration is rather 

 complex and must be attentively considered. Many similar 

 experiments have been offered by Bordet and Gay to demon- 

 strate the function of this bovine colloid substance clearly. If 

 we take washed bovine corpuscles and add to them a mixture of 

 fresh horse serum and heated bovine serum, nothing occurs. But 

 if, in a similar experiment, we use sensitized bovine corpuscles, 

 we find that they become violently agglutinated and are then 

 hemolyzed. This phenomenon is quite identical with the one in 

 Ehrlich and Sachs' experiment on guinea-pig corpuscles. In both 

 instances bovine serum is necessary; neither the bovine corpuscles 

 nor the guinea-pig corpuscles are distinctly altered by the horse 

 serum alone. In the experiment with bovine corpuscles, however, 

 it cannot be asserted that the bovine serum acts as an amboceptor. 

 It must certainly act on account of the particular colloidal substance. 

 Since it is indispensable that such corpuscles should be sensitized 

 and that alexin should be present, the only possible conclusion to 

 be drawn is, that corpuscles that have been sensitized and alexinized 

 are then capable of uniting with bovine colloid, which substance 

 brings about clumping and hemolytic results. The objection may 

 be raised, as indeed Sachs and Bauer have done in their article, 



