74 



PHYSIOLOGY OF BACTERIA 



change, though the streptococcus reduces methylene blue readily. 

 The organism is in need of a hydrogen acceptor, as this reduction 

 proves, but cannot make use of oxygen gas. Methylene blue should 

 have acted as a catalyst, but the small amount of this compound used 

 (0.5 mg. in 100 c.c. of milk) could transfer to the bacteria or their 

 products only 0.028 mg. of oxygen = 0.01 c.c; the process would have 

 to be repeated several hundred times before the oxygen consumption 

 could be detected by this method. 



This agrees with the findings of Callow (see p. 19) that cells of 

 Clostr. sporogenes and Strept. lactis suspended in buffer solution, 

 without food, take up hardly any oxygen, while aerobic and faculta- 

 tive organisms consumed 5 to 25 c.c. of oxygen per hour. The 

 anaerobic organisms lack the faculty to activate oxygen so that it 

 can serve as hydrogen acceptor. 



Quite different was the experience of Meyerhof and Finkle (1925) 

 with Lact. Delhrucki. This organism, though practically anaerobic, 

 consumes oxygen and produces an equal volume of CO 2. For each 

 molecule of sugar oxidized, the fermentation of about six molecules of 

 sugar to lactic acid is prevented. This corresponds with experiences 

 on the metaboHsm of the muscle. 



As in most respiration mechanisms, oxygen consumption was 

 greatly increased by methylene blue, and was retarded by cyanides. 

 With small amounts of cyanide, oxidation could be repressed so that 

 almost equal amounts of lactic acid were formed with air and with- 

 out air. The relative amounts were 



The cyanide had also damaged the fermentation mechanism, but 

 not nearly to the same extent as the respiration mechanism. 



The data of Table 9 can be used only with complete 

 oxidations. For incomplete oxidations, and especially 



