CHEMICAL CONSTITUENTS 293 



the acetyl group might have been introduced into the carbohydrate 

 molecule by the repeated treatment of the substance with acetic 

 acid. Sevag accordingly excluded acetic acid from the method of 

 preparing a special sample and found, contrary to expectations, 

 that the polysaccharide, on analysis, had an acetyl content of 7.7 

 to 7.97 per cent as against the figure of 2.57 per cent obtained by 

 Avery and Goebel. 



It might reasonably be argued, therefore, that Sevag, by a less 

 harsh treatment of pneumococcal cellular material, had succeeded 

 in isolating a polysaccharide that more closely represented the 

 carbohydrate as it naturally exists in the cell than did the prepa- 

 ration of Avery and Goebel. Apparent confirmation of the assump- 

 tion came subsequently with the experimental results of Heidel- 

 berger, Kendall, and Scherp (1936). 627 In searching for a reason 

 for the differences in the immunological behavior of acetylated and 

 deacetylated polysaccharides and from the alkali-treated carbohy- 

 drates of Type II and Type III pneumococci, the authors devised 

 a method of preparation in which the use of heat, strong acid, or 

 alkali was avoided. In general the procedure consisted of the con- 

 centration of culture filtrate in vacuo to a convenient volume; 

 separation of the polysaccharide from salts and protein degrada- 

 tion products by repeated precipitation with alcohol in the presence 

 of sodium acetate and acetic acid; removal of proteins by dena- 

 turation with chloroform and butyl instead of amyl alcohol, as 

 used by Sevag ; and elimination of any glycogen or starch present 

 by methods depending upon the properties of the individual poly- 

 saccharides. The products were isolated as the neutral sodium salts. 



The analytical data on the polysaccharides obtained by the re- 

 vised method present many points of interest when compared with 

 results of analyses of older preparations. In the case of Type I 

 polysaccharide the new product contained 4.62 per cent nitrogen 

 with 2.0 per cent in the amino form, against 5.12 and 2.5 per cent 

 for the old ; showed specific rotation of +278 against +305, the 

 acetyl content was 7.1 as compared to 3.4; it had a higher vis- 



