Precipitins from different Species 147 



pitins, which would scarcely be formed unless there were chemical 

 differences between individuals (see p. 148). 



Working with rabbits, Ascoli (p. 1411) found it impossible to 

 demonstrate any differences in the properties of the antisera they 

 produced, as tested against egg-white solutions with which they had 

 been immunified. On the other hand, when he immunified both rabbits 

 and guinea-pigs with the defibrinated blood of the same dog, he was 

 able to find a difference in the antisera they produced, for on adding 

 the antiserum, say from the rabbit, to dog blood dilutions, until no 

 more precipitation occurred, he found that he obtained a further 

 precipitation on adding antiserum from the guinea-pig. As an ad- 

 ditional proof of the antisera from the rabbit and guinea-pig being 

 different qualitatively, he states that 



Anti-dog serum from rabbit gave a precipituru with normal guinea-pig 1 



but not with normal rabbit. 

 Anti-dog serum from guinea-pig gave a precipitum with normal rabbit 



but not with normal guinea-pig. 



Assuming that Ascoli is correct in this observation, then it is patent 

 that a multiplicity of precipitins are formed in the blood of an animal 

 treated with normal serum of another species. And, moreover, different 

 animals form different precipitins when treated with the blood of the 

 same animal. According to Ascoli, the conclusion seems reasonable 

 (p. 1412) that different precipitins attach themselves to different side- 

 chains of the immensely complex " Rieseneiweissmolekiil," in the sense 

 of Ehrlich. 



1 Concentration not stated. 



10-2 



