RELATIONS OF SENSITIZERS TO ALEXIN. . 371 



detail the logic they have adopted in arriving at their conclusion. 

 Let us follow, then, their argument step by step : First : In order 

 to prove that the sensitizer of heated bovine serum does not com- 

 bine with guinea-pig corpuscles when horse serum is absent, these 

 authors rely on the fact that corpuscles treated with bovine serum 

 remain intact when subjected to horse alexin. Such an argument 

 is valid only on the supposition that horse alexin is capable of hemo- 

 lyzing sensitized corpuscles. Such, however, is not the case. Horse 

 alexin, indeed, differs from the alexins of most sera in this very 

 respect. Ehrlich and Morgenroth have themselves noted* that 

 bovine corpuscles, sensitized by an inactivated hemolytic serum 

 from the rabbit, are not hemolyzed by horse alexin, although very 

 small doses of rabbit or guinea-pig alexin suffice to destroy them. 

 They have explained the fact by saying that the horse alexin does 

 not "fit" the rabbit sensitizer, that is to say, fails to combine with 

 the complementophilic group of this sensitizer; in other words, the 

 alexin is not absorbed by the sensitized cells. It may be noted, 

 however, that this latter fact is not true., for, as we shall later see, 

 the alexin does become fixed by such corpuscles, although it fails 

 to destroy them.f 



There is no proof, then, that because guinea-pig corpuscles treated 

 by bovine serum remain intact in horse alexin, it is due to their 

 not being sensitized, since, when they are undoubtedly sensitized, 

 they give no hemolysis with this alexin. If, indeed, we take guinea- 

 pig corpuscles, sensitized by a specific inactivated serum from the 

 rabbit, we find that, although they are hemolyzed by traces of 

 fresh rabbit serum or even by guinea-pig serum, they remain intact 

 in moderate doses of horse alexin and are destroyed by large doses 

 only after a long period. 



It is, moreover, easy to prove that there is a moderately powerful 

 sensitizer in bovine serum acting on guinea-pig corpuscles in the 

 ordinary way, that is, by uniting with them when no alexin is present. 

 A few tenths of a cubic centimeter of bovine serum (56 degrees) 

 will hemolyze 1 c.c. of a 5 per cent suspension of guinea-pig cor- 



* Ehrlich and Morgenroth, Studies on Immunity, Ehrlich-Bolduan, John 

 Wiley & Sons, p. 88. 



t This fact might be stated in the Ehrlich parlance by saying that horse alexin 

 has no toxophore group or that this group is too weak. 



