380 STUDIES IN IMMUNITY. 



serum. The guinea-pig corpuscles, in other words, may remove 

 all the sensitizer from the bovine serum, since this substance is not 

 necessary in the hemolysis, but they cannot remove the colloidal 

 substance. This colloidal substance is absorbed only by corpuscles 

 that have been treated both with sensitizer and alexin. 



(6) These treated guinea-pig corpuscles that have fixed the 

 sensitizer but not the colloidal substance of bovine serum are not 

 hemolyzed if the excess of serum is removed and horse serum added. 

 Such corpuscles, although they are sensitized and fix the alexin in 

 the horse serum, are not subjected to the effect of the colloidal sub- 

 stance, which has been removed in removing the excess of bovine 

 serum. 



Inasmuch as the preceding experiments, and in particular those 

 dealing with bovine corpuscles, have shown that Ehrlich and Sachs' 

 interpretation formulated on purely theoretical and preconceived 

 grounds is inacceptable, we feel scarcely called upon to consider it 

 further. It is well, however, to verify the accuracy of our own 

 explanation. 



First : We think that the fixation of the colloidal substance occurs 

 only when the corpuscles have been treated with sensitizer and 

 alexin. If this be true we should expect that corpuscles so sen- 

 sitized and alexinized and subsequently carefully washed in salt 

 solution would absorb the colloidal substance of heated bovine 

 serum added to it. We should not expect the presence of free 

 alexin to be necessary for this absorption. 



Inasmuch as clumping is a visible symptom of the absorption 

 of the colloid, we should expect sensitized, alexinized and sub- 

 sequently washed corpuscles to show this phenomenon on the 

 addition of heated bovine serum. In such an experiment -the sen- 

 sitized corpuscles must of necessity not be destroyed by the alexin, 

 and for this purpose horse serum which has only slight hemolytic 

 properties is best. 



We prepare, then, a 10 per cent suspension of ox blood that 

 has been sensitized with a specific serum from the rabbit and 

 subsequently washed, and also a 10 per cent suspension of non- 

 sensitized ox blood. The following mixtures are made in three 

 large tubes: 



