CHEMICAL CONSTITUENTS 249 



— each 0.2; ammonia nitrogen — 1.0; total nitrogen of bases — 5.5; 

 total nitrogen in filtrate from bases — 8.6; phosphorus — 2.92 to 

 2.94 ; chlorine — 0.71 ; and sulfur — 0.32. An absolute alcohol ex- 

 tract of the dried cocci contained 6.5 per cent nitrogen and one 

 per cent phosphorus and was claimed to be entirely free from pro- 

 tein. Water extraction removed material of high phosphorus con- 

 tent, probably of the nature of nucleoprotein, as well as the soluble 

 specific substance. Stull's ether, alcohol, acetone, 0.1N acetic 

 acid, and 0.1N hydrochloric acid extracts all failed to give pre- 

 cipitates with Type I, II, and III antipneumococcic serums. Only 

 the dried cocci, the water extract, and the soluble specific sub- 

 stance precipitated with Type III serum, and here the action was 

 specific. 



It was Avery and Heidelberger's conception that, since Pneumo- 

 coccus is an encapsulated organism, "The ectoplasmic layer of the 

 cell is composed of carbohydrate material which is identical in all 

 its biological characters with the type-specific substance. On the 

 other hand, the endoplasm, or somatic substance, consists largely 

 of protein, which is species- and not type-specific. This protein is 

 possessed in common by all pneumococci, while the carbohydrate is 

 chemically distinct and serologically specific for each of the three 

 fixed types. The cell, therefore, may be conceived of as so consti- 

 tuted that there is disposed at its periphery a highly reactive sub- 

 stance upon which type specificity depends." It was also the au- 

 thors' idea that, since this specifically reactive substance was 

 found to be non-antigenic when separated from the other cellular 

 constituents and was capable of inciting antibody formation only 

 in the form in which it is present in the intact cell, it might be con- 

 cluded that in the latter instance it existed not merely as free car- 

 bohydrate but also in combination with some other substance 

 which conferred upon it specific antigenic properties. 



A tabular representation of some of the immunological functions 

 of intact pneumococci and of their principal constituents is taken 



