ANTIBODIES TO PNEUMOCOCCUS 385 



filtered autolysate which, when injected intratracheally, would 

 kill a guinea pig weighing 200 to 210 grams in from four to 

 twenty-four hours with typical symptoms and necropsy findings ; 

 while one unit of antitoxin represented the smallest amount of 

 serum necessary to protect a guinea pig of the same weight 

 against one unit of toxin when the test toxin-serum mixture was 

 injected intratracheally. Neither normal horse serum nor anti- 

 pneumococcic horse serum containing 500 protective units per 

 cubic centimeter when used in a 1 to 10 dilution exerted a detoxify- 

 ing action on the toxin. A sample of antipneumococcic serum con- 

 centrated by the Felton method, in a 1 to 20 dilution, neutralized 

 the toxin but failed to do so when added in a 1 to 50 dilution. 



The results obtained by Jamieson and Powell (1931) 678 were 

 analogous to those reported by Parker and McCoy. The filtrates 

 of young broth cultures of pneumococci of Types I, II, III, and 

 IV, which had been found to elicit a positive reaction in the skin 

 of rabbits and of human beings, constituted the antigen employed 

 by subcutaneous injection for immunizing horses. The serums de- 

 veloped by the procedure appeared to possess neutralizing sub- 

 stances for the toxin, and these substances could be concentrated 

 to a moderate degree in the refining of globulins by the usual 

 salting-out methods. The concentrated serum contained only a 

 small amount of protective antibody, and in neutralizing action 

 compared favorably with the action of specific antitoxin on scar- 

 let fever streptococcal toxin. 



Employing autolysate prepared by the method of Parker, 

 Blackman 122 produced immune serum in rabbits and horses that 

 would protect normal rabbits not only against the toxic action of 

 autolysate but against pneumococcal infection. 



Sabin (1931) 1208 sought to determine whether antipneumotoxin 

 influences the course of pneumococcal infection in mice. Mice were 

 injected with large doses of Type I and II pneumococci. One 

 series of animals was then treated with therapeutic antibacterial 

 serum, another with antipneumotoxic serum, and a third series re- 



