STUDIES ON AZOTOBACTER CHROOCOCCUM BEIJ. 341 



are placed in contact secrete or produce in the surrounding 

 medium compounds, the nature of which has not been deter- 

 mined. Before attempting to study these compounds we shall 

 enter into a closer analysis of the above experiments. Expressing 

 the quantity of unaccounted for sugar in terms of percentage 

 of the amount of sugar actually disappeared from solution we 

 obtain table 7. 



TABLE 6 



Summary of tables 3 and 5; values obtained in excess of theoretical 



TABLE 7 

 Sugar unaccounted for as per cent of the sugar which disappeared 



It is obvious that no relation whatever exists between the 

 sugar unaccounted for and the CO2 formed in excess of the 

 theoretical, and from table 7 we gather that the addition of 

 nitrogen in the form of Ca (N03)2 has induced a profound change 

 in the physiology of Azotobacter. That the nitrogen is actually 

 consumed during the process of growth could be assumed from 

 the published works of other authors, but to obtain more specific 

 results we may summarize the data obtained on the above men- 

 tioned cultures (table 8). 



The transformation of nearly 10 mgm. of nitric nitrogen into 

 organic nitrogen (which was probably in part organized) is 

 directly connected with the carbohydrate consumption and with 

 the stores of carbon in the cell body and by-products. If such 

 soluble and insoluble material were actually formed it should be 

 possible, by stopping fermentation in its early stages or by an 

 oxygen hunger, to obtain a carbon balance showing a greater 



