CHEMICAL CONSTITUENTS 247 



cal compound. The three types of Pneumococcus chosen for study 

 had, however, when grown on the same medium, yielded three dis- 

 tinct carbohydrates, and successive preparations of each specific 

 substance had been quite uniform whatever methods were employed 

 in the process of purification and whether the preparation was de- 

 rived from pneumococci themselves or from autolyzed broth cul- 

 tures. Furthermore, the only one of these substances investigated 

 in detail appeared to differ in structure from that of any other 

 known non-nitrogenous polysaccharide. It was thought by Avery 

 and Heidelberger that these and other considerations based on the 

 data obtained warranted the belief that the three polysaccharides 

 isolated represented the actual specific substances, stripped of at 

 least a large portion of accompanying impurities, and that the 

 substances did not merely represent inert material carrying an ex- 

 tremely minute amount of the true specific compounds. 



The studies of Heidelberger, Goebel, and Avery also included an 

 investigation of the protein portion of the pneumococcal cell. Hei- 

 delberger, in the reviews already cited, 604 " 5 discussed this phase of 

 the work as follows: 



When these microbes (Pneumococci) are dissolved, either with the 

 aid of bile, or by repeated freezing and thawing, the resulting solution 

 yields a precipitate of so-called "nucleoprotein" on acidification with 

 acetic acid. While probably a mixture consisting largely of nucleopro- 

 tein and mucoid, it still possesses immunological properties which dif- 

 fer sharply from those of the soluble specific substance. In the first 

 place, the protein is antigenic, while the soluble specific substance, 

 though reacting specifically with antibodies to the highest degree, is 

 non-antigenic and unable by itself to stimulate the production of anti- 

 bodies when injected into animals. Moreover, the protein isolated from 

 the three fixed types of Pneumococcus, or from a strain of the hetero- 

 geneous group IV, appears serologically the same as that from any of 

 the other types. Thus this portion of the pneumococcus protein is not 

 type-specific, like the soluble specific substance, but is, rather, species- 

 specific. 



Saito 1213 also prepared nucleoprotein from Type II pneumo- 

 cocci which precipitated with both Types I and II serums and 



