30 



PHYSIOLOGY OF BACTERIA 



coll in 6% peptone solution, and the decomposition of 

 meat extract by Bact. vulgar e, taken from Rubner (1906b 

 and c). 



The results obtained by this method show a fairly good agreement. 

 The average of twelve determinations of the alcoholic fermentation 



Fig. 2. — Rate of heat formation in 1 liter of soil. 



at different temperatures, with sucrose or maltose, with large and 

 small sugar concentrations, with large and small amounts of yeasts, 

 gave the heat liberated from 1 gm. of sugar decomposed by yeast to 

 149.5 cal., the largest deviations being +2.4% and —2.81% (Rubner 

 1904b). This energy corresponds to 26.9 large calories per gram 

 molecule. 



Van Suchtelen (1923, 1927, 1929) improved this method by measur- 

 ing the temperatures thermo-electrically, and by reducing heat 

 conduction. His primary object was the determination of the availa- 

 bility of humus and the rate of its deterioration. He used about 1 

 liter of soil for each experiment, and observed for the first four days 

 a rapid increase in temperature, due to the excess of oxygen intro- 

 duced by the stirring of the soil (see Fig. 2). After twenty days, 

 the temperature had come down to a constant, but was still slightly 

 above the outside temperature, and stayed about 0.3 to 0.6°C. 



