536 A CONTRIBUTION TO THE STUDY OF THE PRECIPITINS, 



The results of this experiment show that in reactions 1 to 12 at 

 quantity of precipitin has not been neutralised by the albumen. 

 In reactions 13 to 16 the precipitin has been neutralised. It 

 also shows that in every tube in which egg-white was present the 

 further addition of antiserum caused a precipitate. On examina- 

 tion of the quantities it will be seen that a quantity of egg-white 

 between 0-000036 gm. and 0-000048 gm. completely neutralised 

 the precipitin in 001 gm. antiserum. The deposits given in 

 Table v., Series A, show that the amount of precipitin decreased 

 in tube 1 to tube 12, and that very little was present in tubes 11 

 and 12. It should be noted that not more than one-fifth of the 

 original precipitin can be ju'esent in the tubes of Series A, and 

 one-fifth of the original egg-white in the tubes of Series B 

 recorded in Table v. The results of these typical experiments 

 have l)een confirmed by comparison with similar experiments. 

 Thus five other series have been made between solutions of fresh 

 and dried egg-white and five other fowl's egg-white antisera (two 

 of which were not dried), one series between ostrich egg-white 

 and dried ostrich egg-white antiserum, one series between the 

 serum of the dasyure and an antiserum for dasyure serum, one 

 series between the serum of the bandicoot and an antiserum pre- 

 pared against the serum of the bandicoot, and one series between' 

 fresh horse and a corresponding antiserum. From similar data 

 Welsh and Chapman* concluded that, for constant quantities of 

 precipitin interacting with varying amounts of homologous pro- 

 tein, the amount of precipitum remains constant as soon as 

 sutticit^nt homologous protein is present to neutralise all the^ 

 precipitin. 



'These experiments serve to determine approximately the 

 quantity of homologous protein which will neutralise the pre- 

 cipitin in a given weight of antiserum. Table vi. records the 

 results obtained. 



It is of interest to record in Table vii., the maximal precipi- 

 tates obtained on complete neutralisation of the precipitin in 

 these anti.sera. 



* .Jouiii. of Hygiene, vi. , p. 259, 1906. 



