BIOCHEMICAL FEATURES 77 



forming activity of the cells was gradually diminished by pro- 

 longed exposure to 55° and was destroyed by heating for five min- 

 utes at 65°. Moreover, cells and extracts of cells thoroughly 

 washed before extraction with salt or phosphate solution showed 

 no peroxide-producing activity, but such extracts could be acti- 

 vated by the addition of cell washings, yeast extract, or muscle 

 infusion. 



In a subsequent paper, Avery and Neill 57 reported that sterile 

 broth extracts of unwashed pneumococci, entirely free from living 

 or intact cells, actively reduced methylene blue, whereas sterile ex- 

 tracts of washed pneumococci in phosphate buffer solution were 

 unable by themselves to reduce the d} T e. As in the case of peroxide 

 formation, the reducing action was restored by the addition of 

 meat infusion or yeast extract to extracts prepared from washed 

 cells. Piatt 1097 reported that meat extract augments the amount of 

 peroxide formed as do also lactic acid and glucose. Gelatin, on the 

 contrary, delays its formation, and in gelatin broth no appreciable 

 amounts of peroxide are present until near the end of the period of 

 logarithmic increase of bacteria. 



The system or systems responsible for methylene blue reduction 

 are destroyed by exposure to temperatures practically identical 

 with those which had previously been found to destroy the per- 

 oxide-forming activity of the same extracts. Avery and Neill 57 sug- 

 gested that peroxide formation and methylene blue reduction by 

 pneumococcal extracts are functions of the same or closely related 

 systems, the particular reaction induced depending upon whether 

 molecular oxygen or methylene blue serves as hydrogen acceptor 

 or oxygen donator. 



In 1930, Hewitt 641 supplied further confirmatory data concern- 

 ing the phenomena of oxidation and reduction by pneumococci and 

 streptococci. In aerobic cultures of both species there is a rise in 

 potential after the logarithmic phase of growth, while in the case 

 of diphtheria bacilli and staphylococci, the potential remains at a 



