STUDIES ON AZOTOBACTER CHROOCOCCUM BEIJ. 335 



Nevertheless, although lactic acid and alcohol could be 

 assumed as by-products of an abnormal physiology of Azoto- 

 bacter, the production of hydrogen and butyric acid suggests a 

 contaminating form.^ 



The fact that Azotobacter gave a ratio C02:02 of about unity 

 in Krzmieniewsky's work does not in itself indicate that all the 

 carbohydrate consumed is utiHzed in a process of combustion. 

 In fact, it is unfortunate that with such a careful study of the 

 gaseous exchange in their cultures these authors were not in a 

 position to present data showing the actual disappearance- of the 

 carbon source from the solutions. 



If we consider the carbon balances in the mathematical terms 

 introduced by Duclaux (1900) we obtain the following equation. 



S = m.L + n.l.t (1) 



where S is the quantity of sugar consumed, L the weight of the 

 cells at the end of the incubation period, I that quantity of cel- 

 lular substance that constitutes the average throughout the 

 period of experiment, m the quantity of sugar actually to be 

 found in the mass of one unit of cellular substance, n that quan- 

 tity of sugar necessary for the maintenance of one unit of 

 cellular substance during the unit of time t. 



Omehansky and Sieber after a study of the composition of the 

 cells of Azotobacter (1913) gro^Ti on agar concluded that cells of 

 Azotobacter contained a relatively small quantity of protein 

 (about 13 per cent), their greater mass being made up of nitro- 

 gen-free substances. It is possible that the heavy "schUme- 

 schicht" that surrounds the cells during the early stages of 

 development should not be forgotten in this connection as also 

 the pecuhar granulations to be found in the cells of this organ- 

 ism (Bonazzi, 1915) and which play a role in their life cycle that 

 is not as yet completely understood. It is possible that such 

 structures are largely made up of that sugar carbon which 

 has been denominated m in the above equation. But as will be 



1 Krzmieniewsky admits of the possibility that the organism which Stoklasa 

 was studying was not Azotobacter. 



