MECHANISM OF DEATH 



307 



by the author for each series. The death-rates have 

 been computed in Table 89 for one day as unit time. 

 The observation that more bacteria survived in oxygen 

 than in air, is contradictory to the other data by Rogers 

 as well as to Paul's results. In all other gases, the 

 death-rate was lower than in air, as was to be expected. 

 The vacuum is the best method of preservation. 



Table 89. — Viability of Dry Lactic Streptococci in Different 



Gases 



The difference in the influence of the various ^' inert'' 

 gases is not explained. The average death-rate in all 

 experiments without oxygen is 0.009 as compared with 

 0.0276 in air. The dry streptococci die in air three 

 times as fast as without oxygen. 



Paul's computation that the death rate is proportional 

 to the square root of the oxygen concentration does 

 not take into consideration this slow death without 

 oxygen. Possibly, the rate was too slow to influence 

 his calculations. However, the fact remains that even 

 with the removal of oxygen, dry bacteria will still die, 

 though more slowly. The cause of death in the absence 

 of oxygen is unknown. 



The simpler method of drying bacteria on filter paper 

 used by Brown (1925, 1926) has not been used for 

 quantitative experiments, but could easily be adapted 

 to this purpose. 



