268 BIOLOGY OF PNEUMOCOCCUS 



the filtrate of a lung obtained at necropsy from a Type III pneu- 

 monia patient. Tested by his whole-blood method, Ward found 

 that a specimen of Type III convalescent blood, though compara- 

 tively weak in anticarbohydrate antibody, was better able to neu- 

 tralize the broth filtrate and lung filtrate than a corresponding 

 mixture of normal blood and antiserum. Two other specimens of 

 Type III convalescent blood neutralized the Type III broth fil- 

 trate. Ward attempted no isolation of this precipitinogen but 

 concluded: "The possibility that the reacting substance in the au- 

 tolysate is more complex and less stable than the carbohydrate — 

 perhaps a substance intermediate between the antigenic carbohy- 

 drate compound in the intact pneumococcus and the carbohydrate 

 itself — was forced on the author as the most likely explanation." 



Evidence which might be taken as indicating the existence of the 

 A substance of Enders, or of some similar principle in Pneumo- 

 coccus, is to be found in the work of Sabin (1931), 1204 who, like 

 Enders, but independently,* attempted to exhaust potent anti- 

 pneumococcic horse serum of protective antibodies by preliminary 

 saturation with homologous SSS and found that in spite of this 

 absorptive treatment the serum still contained an appreciable 

 quantity of the specific protective substance. There appeared to be 

 a lack of proportionality between the quantity of SSS used for 

 precipitation and the amount of protective antibody left in the 

 supernatant fluid. In the reaction some of the protective antibody 

 was evidently lost, since the sum of the precipitated and free anti- 

 bod} 7 represented only from 20 to 50 per cent of the total. This 

 large loss might be accounted for if an excess of specific carbohy- 

 drate were added since it would exert the inhibiting action ob- 

 served by Felton. The same results as those obtained in the in vitro 

 experiments were noted in in vivo tests in the rabbit. f 



Sabin concluded that in antipneumococcic serum there was a 



* Enders' paper was received for publication in May, 1930, and published in 

 August of the same year, while Sabin's communication was accepted in Sep- 

 tember, 1930, and appeared in January, 1931. 



t Incidentally, an observation of interest was that in the combination of SSS 

 with its homologous precipitin there occurred a phenomenon similar to the 



