434 BIOLOGY OF PNEUMOCOCCUS 



strated the protective action of normal human serum for the mouse, 

 while Much* reported that normal human serum, and to a still 

 higher degree, plasma, contained thermolabile bactericidal sub- 

 stances for Pneumococcus. 



Dold (1911), 323 testing by means of plate cultures the action 

 of serum, plasma, and whole blood of normal human beings and of 

 patients ill with diseases other than pneumonia, claimed to have 

 demonstrated definite pneumococcidal effect. The action, stronger 

 in blood than in plasma or in serum, varied from slight inhibition 

 of bacterial growth to actual killing of the organisms. 



According to Clough (1924), 243 normal human beings may pos- 

 sess in their serum substances capable of protecting mice against 

 infection with pneumococci of Types I, II, and III. The degree of 

 protection, when demonstrable, was usually slight, but in five in- 

 stances was sufficient to save the animal from subsequent inocula- 

 tion with 1,000 to 100,000 minimal fatal doses of pneumococci. 

 Protective action against one type of organism was not neces- 

 sarily accompanied by similar action against representatives of 

 other types, nor was the property associated with the presence of 

 any agglutinins or opsonins, since the latter antibodies were ab- 

 sent from the serums tested. 



Burhans and Gerstenberger (1924) 190 tested the serum of in- 

 fants and maternal parents for protective power against Type I, 

 II, and III strains of Pneumococcus. The serum of approximately 

 40 per cent of the parturient mothers protected mice against 

 inoculation with organisms of the three fixed types, while samples 

 of serum from only about 30 per cent of the infants exhibited 

 similar properties. The authors decided that the low incidence of 

 lobar pneumonia during infancy was probably not due to an im- 

 munity to the fixed types of pneumococci. 



Ash and Solis-Cohen (1929) 26 believed that differences in sus- 

 ceptibility to pneumonia among human beings could be deter- 

 mined by the growth-inhibitory and pneumococcidal action of 



* Quoted by Neuf eld and Schnitzer. 



