296 BIOLOGY OF PNEUMOCOCCUS 



plete in its antigenic or chemical constitution as the hypothetical 

 polysaccharide existing preformed in the pneumococcal cell. While 

 Chow's statement may be true that his polysaccharide may be the 

 parent substance from which the acetyl polysaccharide could be 

 obtained by appropriate treatment, there is little doubt that fur- 

 ther search must be made in the lineage of pneumococcal carbohy- 

 drate for the original progenitor of the many derivatives which 

 have been described. 



OTHER PHYSICOCHEMICAL PROPERTIES OF THE CAPSULAR POLY- 

 SACCHARIDE 



Heidelberger and Kendall 618 studied other physicochemical prop- 

 erties of the specific polysaccharides of pneumococci, and deter- 

 mined the viscosity, conductance, and behavior in diffusion of the 

 sodium salts of Type III and other capsular polysaccharides. The 

 high values of the equivalent conductance indicated that the so- 

 dium salt of Type III S* is a strong electrolyte characterized by a 

 mobile negative ion of very high valence. Under varying conditions 

 of salt concentration the authors determined the viscosities of I, 

 II, and III S and correlated the findings with the magnitude of the 

 charge on the anion. The experimental data indicated that at least 

 eight or ten carboxyl groups were present in the molecule at regu- 

 lar intervals of every 340 of molecular weight, so the cumulative 

 effect of the negative charges on the Type III S would be very 

 large, which should result in large interionic or Coulomb forces. 

 These forces were found to be strong. 



The specific polysaccharide of Type I Pneumococcus showed 

 viscosity abnormalities of a similar character, but of smaller mag- 

 nitude. Although its acid equivalent was even lower than that of 

 Type III S, Heidelberger and Kendall thought that internal com- 

 pensation of negative charges by the basic groups present was the 

 cause of the smaller effect. Further data on the specific gum arabic 



* The substitution of the letter S for SSS is consistent with Heidelberger's 

 original usage. 



