256 BIOLOGY OF PNEUMOCOCCUS 



specific polysaccharides. Here again there was manifested that 

 strange difference between immune rabbit and horse serum, the lat- 

 ter failing to sensitize the guinea pigs to the carbohydrate. Both 

 serums precipitate the homologous carbohydrate, but the horse 

 serum fails to bind complement in the presence of capsular poly- 

 saccharide as well as being incapable of rendering guinea pigs hy- 

 persensitive. 



ISOLATION OF C FRACTION 



The existence of another and quite different carbohydrate con- 

 stituent of Pneumococcus was demonstrated by Tillett and Fran- 

 cis. 1409 The authors used as source material a degraded, non-type- 

 specific R strain of Pneumococcus. This particular culture was 

 chosen in order to minimize the presence of type-specific carbo- 

 hydrate. The organisms centrifuged from a full-grown broth cul- 

 ture were suspended in normal salt solution, the cells were frozen 

 and thawed until dissolution was effected, and then, after the addi- 

 tion of acetic acid, the solution was boiled for eight to ten minutes. 

 After removal of the heavy coagulum, acidulation and boiling were 

 repeated in order to remove all acid- and heat-precipitable mate- 

 rial. The final water-clear supernatant fluid contained this new 

 substance which Tillett and Francis called "Fraction C."* 



The C Fraction, although it is probably a nitrogenous sugar, is 

 chemically distinct from both the type-specific capsular carbohy- 

 drate and the somatic nucleoprotein. It exhibits no type-specificity, 

 but yields a precipitate with serum of individuals ill with lobar 

 pneumonia. Following crisis the reaction is no longer demonstra- 

 ble. Furthermore, the precipitation of the pneumococcal Fraction 

 C is not limited to the serum of individuals infected with Pneumo- 

 coccus, since definite reactions can be obtained in streptococcal 

 and staphylococcal infections and in acute rheumatic fever. 



In another communication appearing in the same year, Tillett 



* Tillett and Francis remarked on the similarity of this substance to Lance- 

 field's "Fraction C" which she had obtained from hemolytic streptococci. 



