CHEMICAL CONSTITUENTS 259 



tion of acetylated nitrogen. It differed from the fully acetylated 

 Type IV substance in being broken down by nitrous acid, and dif- 

 fered from all other known specific polysaccharides of Pneumococ- 

 cus in containing phosphorus. 



From this comparative study of the various specific carbohy- 

 drates of Pneumococcus it would seem that these substances fall 

 into two sharply defined groups: on the one hand, the Type II 

 and Type III type-specific polysaccharides, which are nitrogen- 

 free, and on the other, the Type I, Type IV, and C Fractions 

 which contain nitrogen. The two last-named examples in this 

 group, with their content of acetylated nitrogen, are more closely 

 related to chitin than is the Type I substance. In the nitrogenous 

 group, the Type I substance differs sharply from the others in its 

 high optical rotation, its pronounced amphoteric character, its in- 

 solubility at the isoelectric point, its freedom from acetyl groups, 

 and in its high proportion of nitrogen susceptible to attack by 

 nitrous acid. The C Fraction differs from the other members of 

 both groups in its phosphorus content, but resembles the Type I 

 substance in that its specificity is destroyed by nitrous acid ; it is 

 somewhat similar to the Type IV substance in that a part of the 

 nitrogen is acetylated. The Type IV soluble specific substance, on 

 the other hand, differs from the Type I polysaccharide and the C 

 Fraction in containing only acetylated nitrogen and in yielding as 

 high a percentage of reducing sugars on hydrolysis as do the 

 nitrogen-free Type II and Type III capsular polysaccharides. 



The study of the Type IV specific polysaccharide has brought 

 to light a carbohydrate of a new type among those with specific 

 properties. It has, moreover, again been shown that in the closely 

 related pneumococcal types thus far studied, each polysaccharide 

 responsible for type-specificity is different from the others in 

 structure, composition, and properties. The study has also demon- 

 strated the presence in Pneumococcus of a serologically inactive 

 polysaccharide closely related to chitin. This observation points 



