ENERGY SUPPLY OF THE CELL 



29 



bustion heats, all experiments show that the energy 

 actually required was in every experiment at least as 

 large again as the potential energy of the cells produced. 

 Why so much energy is needed, will be explained on 

 p. 32. 



Rubner in his extensive experiments on the energy 

 requirements of microorganisms used, occasionally, the 



flil 



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O.7.* 



oJjcut. cc£i 



Fig. 1. 



3 t ^^^^^^^UMi 



Daily temperature increases in cultures of Bad. coli (6% peptone 



solution), Strept. lactis (milk) and Bad. vulgare (6% meat extract solution), 



same method employed by Tangl, but in most cases 

 considered the direct method of temperature measure- 

 ment to be more accurate. By keeping large amounts of 

 the culture, usually 250 c.c, in a thermos bottle which 

 was placed in a carefully controlled incubator, the 

 temperature increases could be read accurately by means 

 of a Beckmann thermometer. The specific heat of the 

 medium and the heat conductivity of the system were 

 determined and this permitted the thermometer readings 

 to be computed into calories. 



Some typical curves are given in Fig. 1, representing 

 the lactic fermentation in milk, the growth of Bact. 



