460 



COLLECTED STUDIES IN IMMUNITY 



action after one or two washings. We are therefore more inclined 

 to assume that the insusceptibility observed by Flexner and Noguchi 

 is due to a washing out of the activating substances present in the 

 blood-cell. One of us has already reported such extraction phenom- 

 ena (Kyes, 1. c.); we have, however, been unable to repeat the ex- 

 periments. It is possible, as has already been stated, that the 

 divergent results are due to minute differences in the experiment, 

 differences which for the present at least cannot be analyzed. It 

 is also possible that a certain degree of racial divergence in the blood- 

 cells of animals of the same species used by Flexner and Noguchi 

 and by us gives rise to what at present is an inexplicable difference. 

 In the blood-cells employed by us the activating substances could 

 not readily be washed out. This is shown by the fact that the acti- 

 vating substances are so firmly bound to the protoplasm that they 

 are not separated even in preparing the stromata. 



Attention is also called to the antagonism which is so often 

 observed between blood-cells and their own serum. This has already 

 been pointed out by Kyes. Thus rabbit blood-cells are dissolved 

 by cobra venom, and this action is intensified by the addition of 

 rabbit blood-cells which have been made laky. In spite of this, 

 however, the active serum of the same rabbit inhibits cobra- venom 

 haemolysis (see Table XV). In this case, therefore, adherent traces 

 of serum cannot possibly effect autoactivation of the rabbit blood- 

 cells. 



TABLE XV. 



There is another point of considerable interest in connection with 

 these questions, one very important for the technique. The sus- 

 ceptibility of the washed blood-cells can readily be overlooked in 



