CHEMICAL CONSTITUENTS 261 



they become antigenic only when attached to some other substance, pos- 

 sibly the protein of the cell. The type specific character of the anti- 

 genic response, however, is dependent almost entirely upon the nature 

 of the polysaccharide and not upon the substance to which it is at- 

 tached. Therefore, since the specific carbohydrate of the Friedlander 

 bacillus (type B) and that of Type II Pneumococcus exhibit similar 

 chemical properties the antigenic response to each may also be similar 

 even though the proteins or other substances with which they are com- 

 bined are quite dissimilar. 



In 1929, Heidelberger, Avery, and Goebel 608 described the isola- 

 tion of a soluble specific substance from gum arabic (gum acacia). 

 From this gum, which would appear to have no biological relation- 

 ship to Pneumococcus, by partial hydrolysis a carbohydrate was 

 obtained that was comparable to the specific pneumococcal poly- 

 saccharide in its precipitating activity with both Type II and 

 Type III serum. The fraction on hydrolysis yielded galactose and 

 two more complex sugar acids, one of which was later shown by 

 Heidelberger and Kendall 617 to be aldobionic acid and glucurono- 

 galactose analogous to the compounds isolated from the specific 

 polysaccharide of Type III Pneumococcus. 



Another manifestation of heterogenetic specificity was that of 

 the encapsulated strains of Escherichia coli, studied by Barnes and 

 Wight. 87 The organism, isolated from a mouse during a type- 

 determination test on pneumonic sputum, was agglutinated by 

 Type I antipneumococcic horse serum, but not by a similar serum 

 produced in a rabbit. The serum from rabbits immunized with this 

 colon bacillus agglutinated the homologous organism and precipi- 

 tated the soluble specific substance, but failed to cause agglutina- 

 tion of Type I pneumococci or to precipitate Type I pneumo- 

 coccal polysaccharide. In this case the connection was somewhat 

 analogous to that between Type II Pneumococcus and the later 

 Type B Friedlander bacillus of Julianelle. 



Zozaya 1588 published an account of the cross and quite heterolo- 

 gous serological reaction with antipneumococcic serum of dextran, 

 the synthetic polysaccharide produced from saccharose by Leuco- 



