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PHYSIOLOGY OF BACTERIA 



The death rate is influenced remarkably by the medium 

 in which the organisms are heated. In the earlier 

 experiments (Chick, Eijkman) distilled water was used 

 altogether. This introduces considerable uncertainty 

 into the cause of death. Probably, the diffusion of cell 

 constituents into the distilled water is too slow to kill 

 cells in the short time of the experiment. Since the 

 hydrogen ion concentration in distilled water is known to 

 vary greatly, it will not be possible without pH control 

 to obtain data which agree. If these experiments are 

 carried out in a medium suitable for the development 

 of the test organism, there is no chance for variation 

 of acidity, nor for leaching out of essential compounds 

 from the cell. 



A very remarkable observation was made by Lange 

 (1922) namely, that bacteria killed by heat and added 

 to living bacteria, protect these against the action of 

 heat to a remarkable degree. One of his experiments is 



