HE PRECIPITIN REACTION. 323 



the deposits will yield no further precipitate on the addition 

 of antigen. With the same proviso, the weights of the 

 precipitates will be the same and will show the same ratio 

 as the amounts of antiserum, although the quantity of 

 antigen be increased to 200, 300, 400, or 500 mg. or be 

 diminished to 50 mg. These gravimetric experiments 

 demonstrate what our earlier work has indicated (12, 16), 

 that each cubic centimetre of antiserum has a definite 

 " precipitable content " which may be thrown from solution 

 by a certain amount (or concentration) of the antigen. 1 We 

 have already explained that " precipitable content " is not 

 necessarily equivalent to " precipitin," since the " pre- 

 cipitin " may carry down with it non-specific molecules 

 from the antiserum. 



A few illustrative experiments are recorded in the follow- 

 ing Table I. The interactions were conducted in aseptic 

 conditions and were allowed to proceed for 48 or for 72 

 hours, when the deposits were carefully separated, washed, 

 Table I. 





\V..i^.,.,f ' 



25 



^rf 





134 

 134 



2 5 



50 



200 



100 



100 

 100 



