436 BIOLOGY OF PNEUMOCOCCUS 



three subjects exhibited neither property. In another communica- 

 tion, Sutliff with Finland 1360 reported that the incidence of pneu- 

 mococcidal power and of other type-specific antibodies varied with 

 the age of the subject as well as with the different types of Pneu- 

 mococcus. The killing action of normal human serum was most fre- 

 quently observed with organisms of Type II, was rarest for Type 

 I, and was intermediate for Type III strains. 



Gundel, 567 in 1932, investigated the presence of pneumococ- 

 cidins, protective antibodies, and agglutinins in the blood of nor- 

 mal adults and of healthy nurslings and children. The blood of 

 adults frequently showed the presence of definite amounts of anti- 

 bacterial antibodies, whereas no protective or agglutinative action 

 was observed with the serum of new-born babies and young chil- 

 dren. Gundel concluded that antibody formation began in normal 

 children toward the end of the second year of life. Variations in the 

 titer of humoral immunity were manifested in a third or a fourth 

 of the subjects, there being an increase in the case of some indi- 

 viduals and a decrease in others. In the majority of instances the 

 action was specific, since the altered reactivity toward organisms 

 of one type was not accompanied by a similar change toward 

 other types of pneumococci. 



An experimental analysis of the factors responsible for the 

 pneumococcidal action of human serum convinced Ward and En- 

 ders 1484 that in normal human serum virulent pneumococci may be 

 prepared for phagocytosis by two separate antibodies acting in 

 conjunction with complement. One of the substances is probably 

 the type-specific anticarbohydrate antibody reacting with the 

 capsular polysaccharide of Pneumococcus ; the other is probably 

 also a type-specific antibody, but quite distinct from the former 

 and, therefore, reacting with a different antigenic constituent of 

 the bacterium. In normal human serum heated to 56° the two anti- 

 bodies may, after prolonged contact with the organism, promote 

 phagocytosis of pneumococci without the adjuvant action of com- 

 plement. While the two antibodies are equally effective in the 



