436 CHEMICAL DYNAMICS 



no coagulum on heating and yields no precipitate upon admixture 

 with a concentrated solution of the products of the peptic 

 hydrolysis of casein. From these facts they infer that the sub- 

 stance which I believed to have been enzymatically synthesized 

 paranuclein was, in reality, a compound of the heat-coagulable pro- 

 tein contained in Gruebler's pepsin with the caseoses contained in 

 the solution of the products of the peptic hydrolysis of casein. 



While the analytical characterization and identification of a 

 protein substance is extremely difficult and inconclusive, the 

 phenomena of specific immunization, on the other hand, afford 

 us a method of identifying protein substances which, so far as 

 our knowledge at present extends, is decisive and extremely 

 sensitive. The investigations of Wells (75) and of Wells and 

 Osborne (76) have especially demonstrated the high degree of 

 specificity displayed by the immune-bodies which appear in the 

 circulation of animals as a result of repeated administration of 

 foreign proteins. It would appear to be thoroughly established 

 that only protein substances are antigenic, that protein split- 

 products below a certain degree of complexity are non-antigenic, 

 and that the immune-bodies which are developed in response 

 to immunization against a given protein will react only with 

 that protein or with a protein which contains, as an integral 

 portion of its molecule, a large fraction of the molecule of the 

 protein employed in immunization. 



Advantage was taken of these facts by Gay and Robertson 

 (20) to investigate more fully the question of the identity or 

 non-identity of the enzymatically synthesized paranuclein with 

 the paranuclein which results from the partial hydrolysis of 

 casein. They found, employing both anaphylaxis and alexin- 

 fixation as indicators of the development of immune-bodies, that 

 the products of the complete peptic hydrolysis of casein are 

 toxic for normal animals. They have, however, no antigenic 

 property, nor any specific intoxicating effect upon animals sen- 

 sitized to themselves or to paranuclein. Gruebler's pepsin itself 

 is likewise non-antigenic. Paranuclein and the enzymatically 

 synthesized paranuclein, however, both yield specific antibodies 

 and these antibodies react- interchangeably with either substance. 

 These results would appear to yield unequivocal evidence of the 

 occurrence of a genuine protein synthesis under the conditions 

 outlined above. 



