CHAPTER VIII 

 CHEMICAL CONSTITUENTS OF PNEUMOCOCCUS 



The preparation and properties of the protein and carbohydrate 

 fractions of the pneumococcal cell, discussed in relation to their 

 chemical constitution and immunological activities. 



The chemical complexity of pneumococci and the immunologi- 

 cal significance of their constituents were never appreciated, 

 or even suspected, until Heidelberger and Avery 606 announced the 

 results of their study of the composition of these remarkable cells. 

 Like many other bacteria, Pneumococcus had been neglected by 

 chemists. Such information as we had was either based on assump- 

 tion or had come from chance or collateral observations by bac- 

 teriologists. Protein, of course, was present, protein combined 

 with phosphorus being a part of all living cells. Then fats or lip- 

 ids revealed their presence by the fatty acids they yielded on au- 

 tolysis of the cell. Inorganic salts were elements necessary for its 

 vital functions, although there was no detailed knowledge of their 

 kind or quantity. The capsule, so distinctive of the species, had 

 been believed to consist of mucin or some allied substance. It was, 

 therefore, the systematic study of Heidelberger and Avery (1923) 

 which disclosed the presence of the peculiar carbohydrates that 

 give to strains of each type their special serological characters, 

 that spell virulence or, by their absence, lack of virulence, and that 

 determine the exact or specific immunological response the cocci 

 call forth. These studies, moreover, rendered a greater service in 

 revealing a new biological principle, that is, the action of sugars as 

 antigens per se or in orienting the antigenic stimulus of their con- 

 jugated protein, and in their exquisite action as haptens in the 

 presence of homologous immune bodies. 



Carbohydrates had always been disregarded as possessing any 



