SPECIFICITY 1G5 



vcstifiiatecl by \'ic'tor (\ \'auji;liair'' and l)is co-workers, and l)y ImiiII 

 Abdcrhalden, who has demonstrated in various ways an increased 

 proteolytic power in the blood of animals which have received pa- 

 renteral injections of foreign proteins.^" Thus, if the antiserum re- 

 acts on the specific proteins within a dialyzin<!; sac, the products of 

 proteolysis diffuse into the surrounding medium where they can 

 be detected by simple chemical reactions. Also, changes in the spe- 

 cific rotation of the protein or peptid solution can be observed by 

 the polariscopic reading before and after the action of the antiserum. 

 A particularly important corroboration of Vaughan's theory is fur- 

 nished by the behavior of the racemized protein of Dakin. Although 

 soluble, this protein cannot be attacked by the digestive proteolytic 

 enzA^mes, presumably because of its altered configuration; and it is 

 non-antigenic, presumably because it cannot be attacked by the pro- 

 teases of the blood and tissues. Likewise it cannot be metabolized, 

 whether fed or injected subcutaneously.-" Here we have good evi- 

 dence of the fundamental identity of the three processes, digestion, 

 metabolism, antigenic activity. 



As immunity reactions manifest themselves, however, there are 

 steps in the process besides simple hydrolysis of proteins, even if 

 this be the ultimate goal of them all.^^" 



Specificity of Immune Reactions 



The many attempts to explain the various reactions of immunity 

 solel}'' on the basis of known physico-chemical properties of colloids 

 all flatten out when the striking, characteristic, and often extreme 

 specificity of these reactions is considered. Chemical explanations 

 are but little more satisfactory. In enzyme action we find manj^ com- 

 parable examples of specificity, — but this does not help, as the enzymes 

 are as mysterious as the antibodies. But no proposed explanation of 

 any of the reactions incited by antigens can be of value if it fails to 

 take into account the specificity of the reactions. We lack the space 

 here to consider the many ideas and the items of evidence which have 

 been advanced concerning this all-important chemical problem, but 

 refer the reader to the excellent discussion by E. P. Pick.^^ The main 

 facts at present available are the following: Specificity was at first 

 supposed to depend solely upon biological relationships, for it was 

 found easy to distinguish the serum of animals of unlike nature by 

 means of the precipitin and other reactions, but the more closely re- 

 lated the animals the less sharply these reactions distinguish them, 



" See Vaughan, "Protein Split Products," Philadelphia, 1913. 



^^ Abderhalden, " Abwehrferinente des tierischen Organism us," Berlin, 1913. 



" See Ten Broeck, Jour. Biol. Chem., 1914 (17), 369. 



''^" Tadokoro states that immune sera show spectroscopic differences from 

 normal sera .(Jour. Infect. Dis., 1920 (26), 8). 



*' Kolle and Wassermann's Handbuch d. path. Mikroorganismen, 1912 (1), 

 685; full bibliography. 



