392 PHYSIOLOGY OF BACTERIA 



A possible line of attack of this problem is suggested 

 by the experiments of Meyerhof (1916a) who found that 

 a culture of Nitrobacter after having starved for nitrite 

 for twenty hours at 35°C., will oxidize as rapidly as 

 before starvation began; the same culture, after having 

 been without oxygen for the same time, had lost half 

 of its oxidizing capacity. The cell mechanism had 

 evidently been hurt by the long absence of oxygen, 

 but not by the absence of nitrite. 



SUMMARY 



Certain bacteria will die in the absence of food more 

 rapidly when oxygen is removed. This does not hold 

 true for all bacteria. 



If bacteria are cultivated in a medium which cannot 

 be used by them without presence of oxygen, they will 

 die from suffocation soon after the oxygen supply is 

 exhausted. 



XIII. GRAND SUMMARY OF THEORIES OF DEATH 



It can be considered quite well established that dying 

 is a chemical process. On the curve indicating the 

 gradual changes in the cell under adverse conditions, 

 death is not a definite point. Death is a matter of 

 definition. The bacteriologist's definition that death 

 is the loss of reproductive power of the cell is satisfactory 

 for bacteriological purposes; it probably is satisfactory 

 for other purposes as well, as long as the reproductive 

 power of each cell, and not of each organism, is con- 

 sidered. If different definitions of death are chosen, 

 different results might be expected. 



In most cases, bacteria die in a definite mathematical 

 way approaching the logarithmic order closely enough 



