28 COLLECTED STUDIES IX IMMUNITY. 



attack. We have already demonstrated that a hsemolysin, or rather 

 its immune body, is anchored by the erythrocytes, and the solution 

 of the above question therefore becomes very easy. To begin, we 

 have determined that the isolysin behaves like a typical hsemolysin 

 of the well-known kind. It loses its action by being heated for 

 half an hour to 55 C. (destruction of the complement) and is reac- 

 tivated by the addition of a corresponding amount of normal goat 

 serum. 



Next we have determined that the immune body of the isolysin 

 is bound by the susceptible blood-cells in typical fashion; that the 

 blood-cells of the immunized animal, however, take up only traces 

 of the immune body in vitro, amounts far less than those taken up 

 by the almost insensitive blood-cells of goat No. 7. This phenomenon 

 can at once be ascribed to a slight mechanical absorption. We see, 

 therefore, that the serum's own insensitive blood-cells are incapable 

 of anchoring the specific immune body of the isolysin. 



This result can be explained in either of two ways. It may be 

 assumed that the blood-cells lack this receptor entirely, or that, 

 although the cells possess the receptor, the affinity of this had already 

 been satisfied by the immune body in the circulation. In the latter 

 case, however, it is incomprehensible why the blood-cells were not 

 dissolved by the complement also circulating in the blood. Further 

 reasons against the latter assumption will be apparent later, and 

 so we shall at once discuss a series of facts which, according to our 

 views, demonstrate that the insusceptibility of the blood-cells in 

 this case is due to an absolute lack of these receptors. 



Assuming that a given toxin, in an organism, finds receptors 

 which anchor it, the injection of this toxin will be followed by the 

 production of a corresponding antibody. If, however, an organism 

 lack receptors for this poison, the first essential for the production 

 of an antibody will be wanting. In the development or non-develop- 

 ment of antibodies we shall have an indication of the presence or 

 absence of receptors. 



Now, the hsemolysins belong to the class of poisons which pro- 

 duce antibodies. We ourselves have demonstrated that the normal 

 haemolysins of dog's and goat's serum, when injected into a foreign 

 animal body, excite the production of antihsemolysins. The ques- 

 tion was whether the isolysin when injected into the organism of 

 other goats would be able to cause the production of an anti-isolysin. 

 In order to save material we injected a young goat (No. 10), whose 



