1906.] Main Source of " Precipitable" Substance, etc. 



307 



We omitted to test the superfluid of the final interaction with a relatively 

 large amount of egg white, but, doubtless, had we done so, a large residuum 

 of uncombined precipitin would have been revealed. The important fact., 

 however, remains, that the homologous proteid, so far from showing evidence 

 of exhaustion, yields more abundant precipitates at the end than at the 

 beginning of the series, possibly owing to the increasing concentration of the 

 precipitin. 



In the next experiment a similar process of repeated interaction with 

 antiserum was applied concurrently to three tubes containing different 

 amounts of the homologous proteid. 



Experiment VII. — The original amounts of fluid egg white were equivalent 

 in Tube No. 1 to 000006 gramme, in Tube No. 2 to 0-000012 gramme, in 

 Tube No. 3 to - 000024 gramme. Of dried antiserum (prepared by injection of 

 fluid egg white) - 01 gramme was added to each tube, and the same dose was 

 repeated at each successive interaction. The amount of fluid in the original 

 tubes was made up to 1*1 c.c. with salt solution. At each stage the clear super- 

 fluids were transferred by means of a pipette to clean tubes. The amounts 

 were not accurately measured, but about 0'2 c.c. of the fluid was left behind 

 each time. The tubes were 4 mm. in diameter. The results are summarised 

 in Table X :— 



Table X.— Experiment VII. 



No. of 

 interaction. 



Tube 

 No. 



Duration of 

 each interaction. 



Precipita at end of 

 each stage. 







hrs. 



mm. 



1 



1 



48 



1 





2 



24 



1 





8 



24 



1 



2 



1 



48 



1 5 





2 



24 



1 o 





3 



24 



1-5 



3 



1 



48 



1-5 





2 



72 



1 -5 





3 



72 



1 -5 



4 



1 



48 



3 





2 



48 



3 





3 



48 



0-5 



At the conclusion of the fourth interaction the clear superfluids were 

 removed as before, and an amount of fresh egg white (equivalent to 

 - 00024 gramme dried) was added to each. Within 48 hours a large 

 precipitate between 2 - 5 and 3 mm. appeared in each tube, indicating a con- 

 siderable excess of uncombined precipitin. 



