302 Drs. D. A. Welsh and H. G. Chapman. On the [Apr. 30, 



These results indicate that by increasing the amount of precipitin anti- 

 serum there may be obtained precipitates that are enormous relatively to 

 those obtainable from the total amount of homologous proteid in solution. 

 In view of these observations it becomes still more difficult to explain the 

 origin of the precipitate otherwise than from the antiserum. 



When similar observations are carried out with antisera for egg albumins, 

 the results are in accordance with those obtained for horse serum and 

 antiserum. 



Experiment III. — Two corresponding series of tubes were prepared, as in 

 Experiment I, containing from - 0005 to 0*00000005 gramme dried hen egg 

 white in 0"5 c.c. salt solution. To each tube of the first series and to a control 

 was added 0"01 gramme dried antiserum (prepared in a rabbit by injection 

 of dried egg white) previously dissolved in - 5 c.c. salt solution. To each 

 tube of the second series was added 0*5 c.c. of 10-per-cent. trichloracetic 

 acid. The precipitates were read after 48 hours, as shown in Table IV. 



Table IV. — Primary Interactions. Experiment III. 









Precipita in tubes 



Precipita in tubes 





Amount of dried 



Dilutions of dried 



to which -01 



to which "5 c.c. 



No. 



egg white in 



egg white in 



gramme dried 



10-per-cent. 





grammes. 



- 5 c.c. saline. 



antiserum was 

 was added. 



trichloracetic acid 

 was added. 









mm. 



mm. 



1 



-0005 



1 in 1,000 



1 -5 



5 



2 



-00005 



1 „ 10,000 



1 -5 



1 -5 



3 



-000005 



1 „ 100,000 



1 



Minute trace 



1 ' ' '4 



-0000005 



1 „ 1,000,000 



0-3 



None 



5 



-00000005 



1 „ 10,000,000 

 Saline alone 



0-3 



None 



6 



Control 



None 





Again it appears that definite small precipita are obtainable by the 

 interaction with precipitin antiserum of amounts of homologous proteid 

 inadequate to yield a trace of deposit when thrown out of solution by 

 trichloracetic acid. 



After 48 hours one-fifth part of the clear superfluid from each precipitin 

 reaction was transferred to each of two clean tubes, A and B. Series A 

 was tested for residual precipitin by the addition of 0"1 c.c. of 1-per-cent. 

 fresh egg white in salt solution (equivalent to 0-00012 gramme dried) to 

 each tube, while in series B the presence of homologous proteid in excess 

 was revealed by additions of - 01 gramme dried -antiserum in - l c.c. saline. 

 The total fluid in each tube was made up to 0-6 c.c. by addition of salt 

 solution. The precipitates in these secondary reactions were read in 

 48 hours, as in Table V. 



