78 BIOLOGY OF PNEUMOCOCCUS 



low level long after the cessation of active cell proliferation. In a 

 second paper, Hewitt 642 reported the use of liver, blood, or bac- 

 teria in culture media as a means of inhibiting peroxide formation 

 and of permitting the study of other oxidation-reduction phe- 

 nomena. In aerated cultures under these conditions, the potential 

 fell to much lower levels and growth was much more luxuriant. In 

 similar cultures without catalase the potential first declined, then 

 rose to the level at which peroxide can be detected chemically. In 

 the presence of catalase, however, the potential fell, then rose very 

 slowly, and finally reached the level corresponding to peroxide ac- 

 cumulation only after the effective catalase had been destroyed by 

 the active oxidizing system. If fresh catalase was then added an 

 immediate drop in potential occurred. 



Lieb 812 did not agree that the oxidation phenomenon had to do 

 with the formation of hydrogen peroxide but thought that it was 

 due to another mechanism operated by an unknown oxygen-carry- 

 ing factor, possibly a ferment, acting in the same oxygen concen- 

 tration as hydrogen peroxide. Such a conclusion would appear to 

 be no more than conjecture. 



Pauli's work ( 1927-8 ) 1071 was more or less a repetition of that 

 of the American school. He explained the fact that Pneumococcus 

 rapidly undergoes autolysis in cultures by assuming that lysis was 

 due to the production of hydrogen peroxide in the absence of cata- 

 lase. When he grew pneumococci, respectively, in the presence of 

 air, under an atmospheric pressure of thirty millimeters of mer- 

 cury, or under complete anaerobic conditions, the cells grew well, 

 but autolysis took place rapidly in the first, slowly in the second, 

 and was still absent in the third after a month's incubation. Pauli 

 ascribed the advantage of adding any of the many growth-stimu- 

 lating substances to culture media to the content of catalase which 

 decomposes hydrogen peroxide at the time of its formation. 



Another effect of the oxidizing agents formed when sterile ex- 

 tracts of pneumococci are exposed to air is the destructive action 



