HISTORIC DEVELOPMENT OF IMMUNOLOGY 75 



with an equal volume of saturated ammonium 

 sulphate solution which precipitates all the glob- 

 ulins. The solution is filtered; and the globu- 

 lins containing the antitoxin remain upon the 

 filter paper, while the albumins (non-antitoxic) 

 remain in solution and are discarded. The 

 globulin precipitate is now mixed with a sat- 

 urated solution of sodium chloride which dis- 

 solves the portion of the globulin containing 

 the antitoxin, leaving the non-antitoxic portion 

 of the globulin insoluble. The solution is fil- 

 tered and the insoluble portion discarded. The 

 saturated sodium chloride solution containing 

 the antitoxic globulin is now acidulated to pre- 

 cipitate the antitoxin, and the suspension is 

 again filtered. The precipitate containing an- 

 titoxic globulin is pressed to remove the excess 

 of fluid, and is then dialyzed in a parchment 

 bag against running water until the antitoxin 

 is in solution and the inorganic salts are nearly 

 all removed. The reaction and the salt and 

 protein content are adjusted to make the solu- 

 tion isotonic. After dialysis is completed, as 

 shown by chemical analysis, 0.35 per cent tri- 

 kresol is added as a preservative. The solu- 

 tion is then ready for potency tests and steril- 



