BIOCHEMICAL FEATURES 71 



concentration (pH 5.0) attained. Such are the conclusions of 

 Avery and Cullen 37 in their 1919 study. Jones, 6S3 a year later, ex- 

 plained the failure of these authors to produce an acidity greater 

 than a final pH of 7.0 by the fact that they did not add glucose to 

 their beef-infusion medium, but it would seem that this failure had 

 already been accounted for in other parts of their report. 



The degree of acid production by pneumococci appeared to 

 Gundel 569 to be correlated with pathogenicity. He grew strains 

 isolated from human mouths in lactose bouillon (pH 7.0) and in 

 this medium noted only a slight acid formation by pathogenic 

 strains, whereas non-pathogenic pneumococci produced marked 

 acidity with transition forms between the extremes. No confirma- 

 tion of Gundel's results appears to have been published. 



The addition of normal human serum to suspensions of living 

 pneumococci in isotonic bouillon, while preventing cell dissolution, 

 does not inhibit acid production (Lord and Nye 834 ). In rabbit 

 serum, according to Bordet, 139 " 40 the pneumococcidal hydrogen ion 

 concentration is pH 6.2 for Types I, II, and III, and here the 

 acidity is due to formic and acetic acids. 



Oxidation and Reduction 

 Pneumococcus, under varying degrees of oxygen tension, mani- 

 fests the phenomena of oxidation and reduction. With the activi- 

 ties of its oxidases are correlated, either directly or indirectly, 

 synthesis and hydrolysis of pneumococcal protein and carbohy- 

 drates, changes in the hydrogen ion concentration, the formation 

 of peroxide, the conversion of hemoglobin into methemoglobin, the 

 lowering of the oxygen capacity of blood cells, and the death of 

 the organism itself. 



METHEMOGLOBIN PRODUCTION 



In 1913, Butterfield and Peabody, 194 seeking an explanation for 

 the reduction of the 2 capacity of the blood in human lobar pneu- 

 monia, discovered that upon incubating pneumococcal cultures 



