CHEMICAL CONSTITUENTS 277 



fraction was also similar to that of the C Fraction of Tillett and 

 Francis, but Felton ventured no closer comparison of the im- 

 munizing principle in the acid-soluble fraction with the soluble spe- 

 cific substance of Heidelberger and Avery. 



Looking back on the descriptions of the properties of the origi- 

 nal soluble specific substance of Heidelberger and Avery, this ar- 

 ray of diverse pneumococcal carbohydrates was confusing. One 

 wondered which, if any. of these several substances obtained from 

 Pneumococcus actually represented the specific polysaccharide as 

 it existed preformed in the bacterial cell, or which one most closely 

 approached the native substance in its chemical and antigenic fea- 

 tures. There was the possibility, of course, that Pneumococcus 

 might contain more than one constituent of this general type, with 

 differences in individual composition which would account for their 

 special immunological properties. 



CAUSE OF DIFFERENCES IN CARBOHYDRATES ISOLATED FROM 

 PNEUMOCOCCUS 



In the brief communication by Pappenheimer and Enders 1049 

 published in October, 1933, there was a definite clue to the cause of 

 chemical and antigenic differences in some of the various carbohy- 

 drates isolated from Pneumococcus. Enders had previously ob- 

 served that the immunological activity of the A substance was rap- 

 idly destroyed by heating on the alkaline side of neutrality, and so 

 Pappenheimer and Enders surmised that in the method of Heidel- 

 berger and Avery for the preparation of soluble specific substance 

 the A substance was destroyed at the stage where it was precipi- 

 tated with barium hydroxide.* Pappenheimer and Enders, in pre- 

 paring the specific polysaccharide, using the simplified method of 

 Heidelberger and Kendall, 620 accordingly took the precaution of 

 maintaining an acid reaction throughout the process. In this way 

 there was obtained from Type I Pneumococcus an extremely hy- 



* Dudley and Smiths*o also noted that heating with alkali destroyed the pre- 

 cipitating activity of a preparation of pneumococcal polysaccharide made by 

 their method. 



