SPECIFICITY 109 



stimulatinp; the marrow to increased formation of specific antibodies, } 

 e. g., arsenic, mercury and other metals, heliotherapy, hemorrhage^"* ; 

 or phlebotomy, hot baths. 



The other aspect of specificity, i. e., the presence of several antigens 

 in a single organism, each entirely distinct from other antigens in the 

 same organism, has been repeatedly demonstrated. Besides the 

 identification of five distinct antigens in the hen's egg, mentioned 

 previously, we have the repeatedly demonstrated individuality of 

 serum proteins and milk casein of the same animal, and even the dif- 

 ferentiation of casein from lactalbumin in the same milk, as contrasted 

 with the common inter-reactions of caseins from different sources,'^ 

 e. g., cow and goat. A certain but slight distinguishable specificity 

 may be observed between proteins from different organs of the same 

 animal, which differentiation is still sharper between the tissue pro- 

 teins and serum proteins of the animal."^ Sex cells especially seem to 

 be rather distinct immunological!}^ from the body cells. '^^ Numerous 

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

 ing entirely distinct immunological specificities have been described. ^^ 

 Although hemoglobin itself seems not to be antigenic,''® some of the 

 most striking examples of absolute specificity are furnished by red 

 corpuscles, which show readily demonstrable differences between 

 closely related individuals. For example, take the remarkable ob- 

 servation 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. When the mixture of 

 sera was exhausted with the corpuscles of any one of the 110 cattle it 

 would then hemolyze the corpuscles of all the other 109, but was ab- 

 solutely without action on the corpucles of the individual with whose 

 corpuscles it had been exhausted. This indicates that the red cor- 

 puscles 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 b}' Pick, largelj' 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 



'"" See Hahn and Langer. Zeit. Immimitat., 1917 (26), 199. 

 " See Versell, Zeit. Immunitat., 1915 (24), 267. 

 " See Salus, Biochem. Zeit., 1914 (60), 1. 

 "Kiraetz, Zeit. Immunitat., 1914 (21), 150. 



"^ Wells and Osborne, Jour. Infect. Dis., 1911 (8), 66 et seq., especially 1916 

 (19), 183. 



"« Schmidt and Bennett, Jour. Infect. Dis., 1919, (25), 207. 

 " Jour, of Genetics, 1913 (3), 123. 



