ANTIBODIES TO PNEUMOCOCCUS 367 



suits, the precipitate forming immediately without incubation 

 when exudate and serum were of corresponding immunological 



type- 

 There exists more than presumptive evidence that antipneumo- 

 coccal precipitin and agglutinin are the same substance. In a 

 quantitative study of the precipitation and agglutination reac- 

 tions, Heidelberger and Kabat 014 obtained results which seem to 

 prove the truth of the assumption. After removing from a com- 

 bined Type I and II antipneumococcic serum the species-specific 

 antibodies by absorption with somatic protein and the C Fraction, 

 it developed that the application of the quantitative agglutina- 

 tion method of Heidelberger and Kabat and the quantitative pre- 

 cipitation method devised by Heidelberger, Sia, and Kendall 030 and 

 by Heidelberger, Kendall, and Soo Hoo 028 yielded figures, within 

 the limits of the accuracy of the methods, practically identical for 

 anticarbohydrate precipitin and agglutinin. Heidelberger and 

 Kabat stated that while this relation held for unconcentrated 

 serum, in purified antibody solutions somewhat more agglutinin 

 than precipitin was found, which they considered might be due to 

 alteration of a portion of the antibody in the process of purifica- 

 tion. The quantitative correspondence of type-specific anticarbo- 

 hydrate agglutinin and precipitin argues for the immunological 

 and chemical identity of the two immune substances and supports 

 the unitarian theory of antibodies originally formulated by Zins- 



ANTIPROTEIN PRECIPITINS 



The somatic protein of Pneumococcus possesses the property 

 of stimulating the production of precipitin and of reacting with 

 the antibodies so formed. Since the protein is common to pneumo- 

 cocci of all types and to degraded variants as well as to smooth, 

 virulent forms of the organism, its precipitinogenic activity, as 

 might be expected, is specific only for the species and not for type. 

 These facts were reported by Avery and Morgan (1925), M who 



