544 



A CONTRIBUTION TO THE STUDY OF THE PRECIPITINS, 



The results of both series correspond, though the absolute 

 amount of precipitate from each antiserum was different. With 

 a quantity of saline solution of 25 c.c, there was a reduction in 



Table xiii. 



the amount of precipitate. All observers have noted this reduc- 

 tion, which lias been usually ascribed to a solvent action of the 

 concentrated serum. With a quantity of saline solution of 100 

 c.c, the precipitates were also reduced slightly. This reduction 

 was probably due to incomplete reaction in 48 hours, since the 

 superfiuirls removed from tubes 3 and 6 yielded small precipitates 

 on standing for another 48 hours. These results are in accord 

 with the qualitative results previously* obtained. 



Determination of Specific Relations. 



It has alread}' been shown that, under the conditions before 

 described, a given quantity of antiserum gives rise to a certain 

 weight of precipitate, provided a sufficient amount of homologous 

 ])rotein be present. If the protein of the homologous species be- 

 replaced by the protein of a closely related species (as tested by 

 the biological method) the amount of precipitate from that 

 quantity of antiserum is diminished. 



It is not practicable to weigh the precipitate from a given 

 quantity of antiserum interacting wdtli a quantity of unknown 

 pi'otein, as a means of differentiation of proteins. This same 



* Welsh and Chapman, Journ. of Hygiene, vi., p. 256, 1906. 



