370 BIOLOGY OF PNEUMOCOCCUS 



did not preclude the possibility that certain impurities, protein 

 or carbohydrate in character, might have been carried over into 

 the extract. The lack of sharpness in type-specific action would 

 denote the participation of cellular protein in the reaction. 



A precipitin phenomenon described by Boor and Miller 138 in 

 1931 is yet to be explained. Nucleoprotein and non-protein frac- 

 tions prepared from strains of Gonococcus gave precipitates when 

 added to antipneumococcic serum of Types I, II, and III. The 

 antigens were active in high dilutions, and displayed even greater 

 precipitating power in the presence of antimeningococcic serum. 



THE MECHANISM OF SPECIFIC PRECIPITATION 



Gay and Chickering, 508 " 9 in 1914, found that the addition of a 

 water-clear extract of pneumococci to homologous antiserum pro- 

 duces a voluminous precipitate which carries down with it agglu- 

 tinins and the greater portion of protective antibodies. Subse- 

 quently, Chickering 223 found the reaction to be type-specific. In 

 the reaction, therefore, it was evident that the precipitinogen con- 

 sisted of some soluble component of the pneumococcal cell while 

 the specific precipitin, as later shown by Goodner, 528 was a sub- 

 stance associated with the euglobulin of the horse serum employed. 



Soluble specific substance. Heidelberger and Avery, 606 in 1923, 

 isolated the soluble specific substance from Type II pneumococci 

 and announced that it consisted mainly of a carbohydrate and 

 that in as high a dilution as 1 to 3,000,000 gave positive precipi- 

 tation with homologous antiserum. According to the authors, the 

 precipitinogen was apparently a polysaccharide constituting the 

 capsular substance of Pneumococcus. This important conclusion 

 was the first evidence of a possible connection between the capsular 

 material and the specific relationships of pneumococci, and ac- 

 counted for the type-specificity of the precipitin reaction. 



Felton and Bailey 420 fully substantiated the work of Gay and 

 Chickering on the nature of the precipitate, and also the observa- 

 tion of Heidelberger and Avery 607 that a single component of 



