404 Dr. H. G. Chapman. On the Weight of [Apr. 21, 



the superfluids removed from tubes Nos. 3 and 6 yielded small precipitates 

 on standing for another 48 hours. 



Table V. 



No. of 

 tube. 



Amount 

 of antiserum. 



Weight 

 of egg-white. 



Amount of 

 saline solution. 



Weight 

 of precipitate. 



Weight of pre- 

 cipitate from 

 1 c.c. antiserum. 





c.c. 



milligrammes. 



c.c. 



milligrammes. 



milligrammes. 



1 



5a 



100 



25 



10 -8 



2-2 



2 



5a 



100 



50 



16 -2 



3-2 



3 



5a 



100 



100 



15 -0 



3-0 



4 



5b 



100 



25 



10 -6 



2-1 



5 



5b 



200 



50 



19 -5 



3-9 



6 



5b 



400 



loo 



17 -7 



3-6 



The results recorded above are typical of those obtained by the examina- 

 tion of 23 different antisera. The amounts of precipitate obtained from the 

 various antisera showed much variation. The quantity of homologous 

 protein required to precipitate completely the precipitin showed similar 

 variations. The gravimetric results confirm the volumetric results of Welsh 

 and Chapman* as to (1) the amount of precipitable substance in an anti- 

 serum, and (2) the amount of homologous protein necessary to neutralise 

 and precipitate this precipitable substance. The quantity of precipitate 

 obtained from 1 c.c. antiserum on the complete precipitation of the 

 precipitable substance of the antiserum is recorded in Table Vl.f 



The results show that the weight of precipitate varied from 0'8 milligramme 

 to 4"3 milligrammes from each cubic centimetre. 



Remarks on the Experimental Results. 



When an amount of antiserum, e.g. 3 c.c, interacts in suitable dilution with 

 increasing quantities of homologous protein, the weight of the precipitate 

 augments as the quantity of homologous protein taking part in the inter- 

 action is increased (Table IV). The rate of increase in the weight of the 

 precipitate is rapid as the quantity of homologous protein rises from minute 

 quantities to 5 milligrammes or 10 milligrammes, the e.xact amount varying 

 with different antisera. With further increments of homologous protein this 

 rate of increase is diminished. When the quantity of homologous protein 

 reaches from 30 milligrammes to 100 milligrammes (the exact amount varying 

 with different antisera) any increase in the weight of the precipitate ceases. 



♦ ' Jouni. of Hygiene,' vol. 6, p. 262, 190G. 



t An analysis of the effect of the various factors of the process of immunisation on the 

 weight of the precipitate will be published later. 



