SPECIFICITY 167 



other pure proteins iiecordiiifi; to whether chemical dijfferences can 

 be demonstrated by recognized analytical methods. 



A striking example of the existence of identical antigenic prop- 

 erties in materials of biologically unrelated origins, is furnished by 

 the sheep corpuscle ti^|nn1ys:Ln discovered by Forssner,^* who found 

 that man}^ different materials, \vhen injected into rabbits, engender in 

 the rabbits' serum active hemolytic amboceptors for sheep corpuscles. 

 This antigenic property has been demonstrated in the organs of the 

 guinea-pig, horse, cat, dog, mouse, chicken, turtle, and several species 

 of fish,''^ although not exhibited by organs of many closely related 

 species (e. g. pig, ox, rabbit, goose, frog, eel, man, pigeon, rat). It is 

 not present in the red corpuscles of these animals, but is present in 

 the corpuscles of the sheep, whose organs do not have this property. 

 It has also been found in paratyphoid and Gartner bacilli, mouse 

 tumors and sheep spermatozoa. Not only does the serum of rabbits 

 thus immunized show active hemolysis for sheep corpuscles, but if 

 injected into the vein of an animal whose organs contain this antigen 

 there results a prompt, severe anaphylactic intoxication, presumably 

 through reaction between the antigen present in their tissues and the 

 antibodies of the rabbit serum. Furthermore, the antibody can be 

 specifically removed from the immune rabbit serum by contact with 

 any of the antigen-containing tissues, but not by tissues that do not 

 exhibit this antigenic property. The antigen seems to remain in the 

 tissues when the fluids are forced out by pressure, and Doerr and Pick 

 believe it to be associated with the nucleoproteins. 



This series of observations, which seem to have been quite gen- 

 erally corroborated, indicates conclusively that the immunological 

 specificity of an antigen is not necessarily related to the biological 

 specificity of the living organism from which it is derived. The logi- 

 cal explanation is that there may exist proteins in different species 

 which have chemical resemblances or identity, and this is scarcely to 

 be doubted. We find identical lipoids, fats, nucleic acids, and carbo- 

 hydrates in different species; many peculiar types of proteins show 

 apparent chemical identity in different species (e. g. gelatin, keratin) ; 

 some chemically similar, derived proteins also seem immunologically 

 identical or closely related (e. g. lens protein, casein). Therefore, it 

 is highly probable that many tissue proteins may be identical in dif- 

 ferent forms of animal cells, and even in animal and plant cells. 



Another sort of manifestation of apparently non-specific immunity 

 reactions has been observed especially in therapeutic immunization.^® 

 Beginning with the classical observation of Matthes that the tuber- 

 culin reaction could be produced with deutero-albumose, many sim- 

 ilar non-specific reactions have been observed. Particularly the 



" Review by Doerr and Pick, Biochem. Zeit., 1914 (60), 257. 



" Tsunecka, Zeit. Immunitat., 1914 (22), 567. 



^« See review by'Jobling, Jour. Amer. Med. Assoc, 1916 (66), 1753. 



