RELATIONS OF SENSITIZERS TO ALEXIN. 369 



nothing remarkable in the experiment. But in a second experiment 

 the corpuscles are placed in contact with the ox serum, and after 

 a certain period the mixture is centrifugalized and the supernatant 

 fluid decanted. On the addition of horse serum to the sedimented 

 corpuscles no hemolysis takes place. It would seem, then (and 

 such is the conclusion of Ehrlich and Sachs), that the corpuscles 

 have failed to absorb the sensitizer from the ox serum in spite of 

 contact with it. This conclusion seems further corroborated by the 

 fact that the supernatant fluid that has been used in treating the 

 corpuscles is just as active as before contact. Fresh guinea-pig 

 corpuscles when added to this supernatant fluid plus fresh horse 

 serum are readily hemolyzed. And, what is more, the treated cor- 

 puscles, which are not hemolyzed by fresh horse serum alone, are 

 destroyed as readily as fresh corpuscles by a mixture of heated ox 

 serum and horse alexin. 



Ehrlich and Sachs' interpretation as already stated is as follows : 

 The bovine sensitizer unites readily with the corpuscles as soon as 

 its affinity for alexin (horse) is satisfied, in other words, when its 

 complementophilic group is saturated. This is the reason that 

 hemolysis takes place in a mixture of the two sera. But the sen- 

 sitizer shows little or no affinity for the corpuscles unless previously 

 combined with the alexin. This explains why the corpuscles remain 

 intact when treated successively with ox serum and then with 

 horse serum. If these interpretations are correct, as Ehrlich and 

 Sachs affirm, we are forced to admit that a saturation of the com- 

 plementophilic group by means of alexin increases the chemical 

 affinity of the cytophilic group, in other words, the affinity for the 

 corpuscles. 



Theoretically, it is rather difficult to conceive of such a repercus- 

 sion as this, since, according to Ehrlich's theory, the two atom 

 groups are distinct and independent. It is better at all events to 

 remain within the bounds of experimentation. The experiments 

 which we have just mentioned are the only ones that Ehrlich and 

 Sachs have referred to. As we shall see, it would have been prefer- 

 able for them to have investigated somewhat further and to have 

 adduced other experiments before offering their interpretation. 



There is one fact in particular which, although remarkable and 

 certainly of significance in any correct interpretation, seems to have 



