FURTHER DEVELOPMENT OF KNOWLEDGE 193 



Gay, 8990 also, though he was the first definitely to associate 

 precipitin formation with the alexin-fixing property and, indeed, 

 determined a rough parallelism between the amount of precipitate 

 and the degree of alexin fixation, has nevertheless recently declared 

 himself in favor of the assumption of the presence in protein anti- 

 sera of two antibodies, the alexin-fixing lysins and the precipi- 

 tins. This he does on the basis of certain experiments from which 

 he concludes that the antigen-antibody complex which fixes alexin 

 is distinct from the precipitin-precipitinogen complex, but is usu- 

 ally "brought down in its formation in such a way as to simulate 

 fixation by the precipitate." Nicolle 91 goes even further than 

 this in declaring that the "coagulins" or precipitins are "anti- 

 corps bons," which prevent the action of the albuminolysin upon 

 the antigen, thereby inhibiting the liberation of poisonous cleavage 

 products. 



It seems to the writer 9293 that the assumption of a separation 

 between the precipitin and the albuminolysin is a needlessly compli- 

 cated interpretation of the phenomena. In order to elucidate this 

 point a comparison was made between the fixing properties of a 

 mixture of a protein (sheep serum) and its antibody and a mixture 

 of typhoid filtrate and antityphoid serum in which it is known that 

 both precipitins and antibacterial sensitizers are present. It was 

 shown that, as stated before, in the former mixture the alexin-fixing 

 property resided entirely in the precipitate, whereas in the latter 

 case both the precipitate and the supernatant fluid fixed a-lexin. 

 From this it seems to follow that immunization with the more com- 

 plex cellular elements has given rise to the precipitating antibody 

 present also in the antisheep serum, and, in addition to this, to sensi- 

 tizers which are not precipitable (remaining in the supernatant 

 liquid) and not present in the antisheep serum. The precipitates, 

 moreover, were found to fix "end-piece" and "mid-piece," frac- 

 tions of alexin, in the same way as these are fixed by sensi- 

 tized cells. 



Without going into further complicated detail, it would seem to 

 us 94 to be justified that we look upon the so-called precipitins not as 

 separate antibodies but as identical with so-called albuminolysins. 

 They unite with the antigen, producing an alexin-fixing complex. 

 Since both reacting bodies are colloidal in nature, they precipitate 

 each other in the test tube, but, following the laws governing other 

 mutually precipitating colloids, they do so only when brought to- 



89 Gay. Loc. cit. 



90 Also Univ. of Cal PuU. in Pathol., Vol. 2, No. 1, 1911. 



91 Nicolle. Ref. in Bull, de I'Inst. Past., Vol. 5, 1907. 



92 Zinsser. Journ. Exp. Med., Vol. 15, 1912. 



93 Zinsser. Proc. of Soc. of Exp. Biol. and Med., April, 1913. 



94 Zinsser. Journ. of Exp. Med., Sept., 1913. 



