MECHANISM OF DEATH 383 



Check experiments were made with broth. Table 125 gives the num- 

 bers of survivors, in percentages. 



It is quite evident that Bad. coli is the only one of the organisms 

 tested which can survive in distilled water for any length of time. 

 It should be borne in mind, therefore, that results on starvation with 

 Bad. coli are exceptional cases, and must not be generalized. 



These authors then determined the limits of dilution which would 

 keep cells of B. cereus alive for one hour after centrifugation, and 

 found that broth diluted 1:100 protected the bacteria perfectly, 

 broth diluted 1:1,000 only for a short time. Ringer's solution, and 

 sugar solutions of different concentration offered no protection. A 

 peptone concentration of 0.005% or a meat extract concentration 

 of 0.003 % kept the cells alive, but one-tenth of these concentrations 

 caused a rapid reduction of living cells. 



Death in the last experiments is so rapid that it cannot very well 

 be explained as being caused by starvation. Since Ringer's solution 

 and isotonic sugar solution offered no relief while colloids in very low 

 concentrations sufficed to save the life of the cells, it seems quite 

 possible that some toxic compounds were contained in the distilled 

 water which were absorbed or chemically bound by the colloids. 

 That bacteria will die from starvation within one hour is quite 

 improbable. 



(c) STARVATION FROM LACK OF NITROGENOUS FOOD 



Chemical changes taking place in starving cells have 

 already been discussed in Chapter I, on pp. 10 to 18. 

 Those experiments refer mostly to yeast kept in a sucrose 

 solution without nitrogenous compounds. These are 

 the only experiments known to the author as referring 

 to death in the presence of fermentable material, or 

 energy food, but in the absence of nitrogenous material. 

 They correspond to experiments on protein-free diet with 

 animals. 



Two experiments by Rubner (1913) are sufficiently 

 detailed to give data for the computation of successive 

 death rates. In both experiments, the yeast remained 

 for twenty-four hours in a 10% sugar solution, was then 



