400 BIOLOGY OF PNEUMOCOCCUS 



mococci. In in vitro phagocytic experiments with human blood, 

 antipneumococcic serum, capsular polysaccharide, and living, 

 virulent pneumococci, there was a zone of definite phagocytic 

 inhibition when a strong antiserum was used. Upon dilution of the 

 serum there appeared a zone in which phagocytosis was effective. 

 Ward suggested that the inhibition was caused by the specific pre- 

 cipitate formed by the combination of soluble specific substance 

 and precipitin, which interfered, perhaps mechanically, with the 

 ingestion of the pneumococci by leucocytes. 



In later reports, Ward 1482 " 3 described a type-specific substance 

 with a powerful antibacterial action present in the filtrate of a 

 five-day broth culture of Type III Pneumococcus. A similar sub- 

 stance was also demonstrated in the filtrate of a lung obtained at 

 necropsy from a patient dying of lobar pneumonia caused by a 

 Type III organism. Ward employed a method devised by himself 

 for estimating the pneumococcidal action of whole blood, and 

 found that if the precipitinogen content of the broth filtrate and 

 the amount of soluble specific carbohydrate of Type III Pneumo- 

 coccus were taken as a basis of comparison, it required approxi- 

 mately one thousand times as much antiserum to neutralize the 

 antagonistic action of the broth filtrate as was necessary to neu- 

 tralize the specific carbohydrate. Ward also found that a specimen 

 of blood from a patient convalescing from Type III lobar pneu- 

 monia, though comparatively weak in anticarbohydrate antibody 

 (precipitin), was better able to neutralize the broth filtrate and 

 the lung filtrate than a corresponding mixture of normal blood and 

 specific antipneumococcic serum. 



Enders and Wu (1934) 362 more recently reported that the op- 

 sonic titer of normal serum could be practically abolished by the 

 addition of the A carbohydrate. In immune serum, the A sub- 

 stance brought about a quantitatively greater reduction in op- 

 sonic activity than did its derivatives, but the authors were never 

 successful in demonstrating complete inhibition of phagocytic ac- 

 tion by the method of absorption of antibody. Enders and Wu also 



