CHEMICAL CONSTITUENTS 295 



The susceptibility of the capsular polysaccharide to even fairly 

 rigorous chemical treatment has been shown further in the case of 

 the soluble specific substance of Type III Pneumococcus by Hor- 

 nus and Enders. 656 By avoiding as far as possible the use of strong 

 acids in the isolation of the carbohydrate a preparation was ob- 

 tained that gave a precipitate with Type III immune serum after 

 the serum had been absorbed by Type III SSS made by the earlier 

 method of Heidelberger and Avery. The sample contained 0.3 per 

 cent nitrogen and in this respect resembled the material described 

 by Heidelberger, Kendall, and Scherp, 626 but it differed in some of 

 its serological properties. 



The gap between the polysaccharides as derived by chemical ma- 

 nipulation and the native substance in the pneumococcal cell is be- 

 ing still farther narrowed. By omitting the preliminary autoclav- 

 ing of pneumococcal cultures, by leaving out alkaline treatment, 

 and employing a method that minimized hydrolysis by acid or 

 alkali, Chow 225 obtained a polysaccharide from Type I Pneumo- 

 coccus that gave a precipitate with homologous immune rabbit se- 

 rum previously absorbed with the acetyl polysaccharide. The ace- 

 tyl polysaccharide failed to react with homologous immune rabbit 

 serum after absorption by the new carbohydrate. The greater ab- 

 sorptive power of the new preparation as compared with that of 

 the acetyl polysaccharide suggests its possession of a group or 

 radical which was lacking in the acetylated derivative, but the fact 

 that antipneumococcic serum absorbed with the new preparation 

 was still agglutinative and specifically protected white mice against 

 an otherwise fatal dose of Type I Pneumococcus may be taken to 

 indicate that the carbohydrate isolated by Chow is not so com- 



charide. The details of the preparation of the medium are given in the Ap- 

 pendix. 



The use of peptone instead of meat as recommended by O'Meara and Brown, 

 according to an unpublished personal communication of Heidelberger, greatly 

 facilitates the preparation of both the capsular polysaccharide and the C car- 

 bohydrate. The C Fraction can be easily isolated from the supernatant fluid of 

 such a broth after removal of the capsular polysaccharide. 



