This we have expressed l>y saying tlmt antisera are charac- 

 terised by different degrees of precipitability (12, 1G). When 

 the antigen is insullieient u> give the maximal precipitate 

 from the antiserum, then the interaction is only partial, 

 and further additions of antigen will continue to give 

 further precipitates until the full precipitate has been 

 thrown out. Many precipitin antisera are characterised 

 by high precipitability, and are therefore likely to give 

 such partial interactions. 



Our earlier experiments on these lines, based on the 

 volumetric estimation of small precipitates, are supported 

 by our later results of weighing larger precipitates. Two 

 illustrative experiments are given in Tables II and III. In 

 each experiment constant volumes of an antiserum (pre- 

 pared in a rabbit with hen egg-white) were allowed to 

 interact with increasing weights of antigen (dried hen egg- 

 white), and the precipitates at 48 hours were washed, dried 

 :| ud weighed. A dilTerent hen rii^ antiserum was used in 

 each experiment. 



N „. 





^r' \~°°\ -IF ' : 



1 



I 



1 44 I 50 10 33 

 7-2 : 50 2-0 0-67 



In the first experiment (Table II) the amount of deposit 

 continued to augment with each increase of the antigen, 

 and the whole of tiie precipitable substance was not thrown 

 out of 3 cc. of the antiserum by nearly 29 mg. of the anti- 

 gen. This antiserum is characterised by a considerable 

 Precipitable content (at least 2*2 mg. per cc. of antiserum), 

 and high precipitability. It is just the kind of antiserum 



