SPECIFICITY OF IMMUNE REACTIONS 175 



rather distinct iminnnol()<iically from the body cells. ■'^° Numerous 

 instances of two separate proteins from the same plant seeds show- 

 ing entirely distinct immunological specificities have been de- 

 scribed/^'* On the other hand, hemoglobins which the crystallo- 

 graphic work of Reichert has shown to be remarka])ly specific from 

 that standpoint, seem to show an equally marked si)ecies specificity 

 when tested by anaphylaxis.^^' Indeed, some of the most striking 

 examples of absolute specificity are furnished by red corpuscles, which 

 show readily demonstrable differences between closely related indi- 

 viduals. For example, take the remarkable observation of Todd,*^^ 

 who mixed together isolytic beef sera from over 60 animals, and then 

 tested the mixture with the corpuscles of 110 different cattle, all of 

 which were hemolyzed. But when the mixture of sera was ex- 

 hausted with the corpuscles of any one of the 110 cattle it would 

 then hemolyze the corpuscles of all the other 109, but was absolutely 

 without action on the corpuscles of the individual with whose cor- 

 puscles it had been exhausted. This indicates that the red corpuscles 

 of any individual possess characters which differentiate them from 

 the corpuscles of any other individual even of the same species. 



As satisfactory a conception of the nature of specificity as our 

 present evidence warrants is that developed by Pick, largely on the 

 basis of his own work. He properly accepts the influence of both 

 the physico-chemical properties and the chemical composition of the 

 colloids concerned in immunity reactions as determining specificity. 

 Both these factors undoubtedly come into play in determining the 

 possibility of interaction of antigen and antibody. The electric 

 charges of the amphoteric colloidal antigen and antibody, and per- 

 haps also their surface configuration and their surface forces, all 

 influence their reaction ; these physico-chemical factors greatly com- 

 plicate the possibility of reaction between two colloids, and to these 

 influences are added the influence of the chemical structure in deter- 

 mining subsequent chemical reactions. It would seem possible that 

 the existence of all these factors may account for specificity, it being 

 necessary for each one of a long series of both physical and chemical 

 adjustments to agree perfectly in order that reaction may take place 

 — just as in a combination lock one lever after another is thrown by 

 the i)roper manipulation of the dial, and only when all the long series 

 of levers is in just the proper position does the bolt engage and the 

 lock open." 



The studies of Pick and his colleagues, amplified somewhat by other 

 investigations, have led to the following view of the chemistry of 



4igGraetz, Zeit. Immunitiit., 1014 (21), 150. 



4ih Wells and Osborne, Jour. Infect. Dis., 1911 (8), GG et sen., especially lOlG 

 (19), 18.3. 

 4ii Bradley and Sansum, Jour. Biol. Cliem., 1914 (18), 407. 

 4ij,Jour. of Genetics, 1913 (3), 123. 

 42 The "resonance tlieory" of Traube assumes tliat the surface forces of react- 



