SECTION 11. 



THE NATURE OF PRECIPITIN REACTIONS. 



That the precipitins are used up in the process of precipitation, was 

 already observed by Myers (14, vii. 1900) who took it as evidence of 

 the action being chemical in nature. Michaelis and Oppenheimer 

 (1902, p. 357) consider that the precipitins cannot be regarded as a 

 special form of coagulative ferment for the reason that they are used 

 up quantitatively in considerable amount. Whereas, it is true, that 

 ferments are also ultimately used up, this occurs but slowly and in a 

 very slight degree as compared to the amount of substratum affected. 

 Precipitins are used up in a manner analogous to what takes place when 

 toxin is added to antitoxin, or acid to base. 



Eisenberg (5, v. 1902) following Ehrlich's absorption method, deter- 

 mined the amounts of the mixed interacting substances, before and after 

 reaction had taken place. In this way he was able to find that both 

 substances combine quantitatively, for measureable amounts of both 

 had disappeared from the mixture. The results of Mliller (1902) and 

 of Leblanc (1901) with lactoprecipitins and haemoglobinprecipitins gave 

 similar results, pointing to the fact that both substances are present in 

 the precipitum. Eisenberg therefore adds that Halban and Landsteiner 

 (1902) are scarcely justified in denying the chemical nature of the 

 reaction. These authors claim in proof of this that salt-free serum 

 albumin heated to 100" C. partly loses its precipitability, although it 

 contains as much albumin as before. It may well be said in rejoinder 

 that this was no longer native albumen. I have stated elsewhere 

 that the precipitins act independently of the amount of albumen, the 

 latter must therefore possess certain specific properties if they are to 

 combine with the precipitins. 



In this connection it is of interest to cite some very careful analyses 

 and tests made here by Mr F. G. Hopkins, to whom I am exceedingly 



