228 PROTEIN POISONS 



act as exquisite sensitizers. Moreover, it has been found 

 that the more thoroughly a protein is purified the more 

 perfectly it sensitizes and the smaller the dose necessary 

 to sensitize or to kill on reinjection. Wells found that 

 purified casein acts more perfectly and in smaller doses 

 than a corresponding quantity of milk, and the sensitizing 

 dose of crystallized egg-white is less than one one-hundredth 

 that of native egg-white, and the killing dose on reinjec- 

 tion less than one-fifth. These facts have led Wells to 

 suggest that the mixed albumins may contain substances 

 which antagonize the anaphylactic reactions. Since pure 

 proteins sensitize and kill on reinjection, it seems reasonable 

 to conclude that the sensitizing and poisonous groups are 

 constituents of the same molecule. Edestin in its most 

 highly purified form is believed to be a chemical unit, and 

 not a mixture of proteins. This can be split by our method 

 into sensitizing and poisonous portions. It is true that the 

 amount of the non-poisonous portion necessary to sensitize 

 is larger than that of the unbroken molecule necessary to 

 accomplish the same purpose, and it is possible that sensi- 

 tization with this product is due to the fact that it contains 

 a trace of the unbroken molecule, but the fact that no 

 amount of this portion induces the slightest anaphylactic 

 symptoms on reinjection is not in harmony with this view. 

 It seems more reasonable to assume that in the process of 

 cleavage, which is crude, a large part of the sensitizing 

 group is destroyed. It is certain that the poisonous portion 

 does not sensitize to either itself or the unbroken molecule. 

 By our method the molecule is disrupted and in so doing 

 both portions are largely destroyed. The final word on 

 this matter cannot be spoken until we know that we have 

 absolutely pure proteins to start with, and we have more 

 perfect methods for the cleavage of the protein molecule. 

 However, it seems certain that the sensitizing properties 

 of the protein molecule reside in a group or in groups which 

 are destroyed by digestion long before the poisonous group 

 is markedly impaired. The sensitizing group seems more 

 labile than the poisonous one. 



