164 Precipitum obtainable in Precipitin Interactions, ete. 
Conclusions. 
These observations reinforce our previous conclusions* regarding certain 
phenomena of precipitin reactions by showing :— 
(1) That the homologous protein is capable of throwing out of solution 
many times its weight of precipitum, and 
(2) That, in the interaction of minute quantities of homologous protein 
with large amounts of antiserum, the protein is not completely removed from 
the superfluid, but that sufficient remains to produce a second, and also to 
produce a third interaction with similar large amounts of fresh antiserum. 
It is apparent, therefore, that the serum (antiserum) of a rabbit, immunised 
with egg-white or with blood serum, acquires the capacity, not so much of 
precipitating, as of being precipitated by the homologous protein; in other 
words, that the antiserum, and not the homologous protein, is the main 
source of “precipitable ” substance. 
We desire to acknowledge the courtesy of Professor Anderson Stuart in 
placing his laboratory at our disposal. 
* Welsh and Chapman, ‘ Roy. Soc. Proc.,’ B, vol. 78, p. 312, 1906. 
