334 AUGUSTO BONAZZI 



To reconcile this work with the statements of Omehansky and 

 Sewerowa (1911) is impossible if we assume both groups of 

 workers to be working with pure cultures of the organism in 

 question. Although statements as to the purity of his cultures 

 were made by Stoklasa, the fact that hydrogen in the free state 

 was found to be generated in appreciable quantities, as well as 

 butyric acid, in some cases, would tend to make this purity 

 questionable. 



If now we consider in this connection the work of Krzmieniew- 

 sky (1908) we have a series of most interesting data that bring 

 out two very striking features: 1, complete lack of hydrogen 

 production and, 2, striking difference in the 000:02 ratios result- 

 ing from the utilization of glucose and mannitol. One feature 

 of this work which deserves special attention is that the ratio of 

 CO2 formed to nitrogen fixed is not constant. Expressed in 

 other words there does not exist a constant C :N ratio for Azoto- 

 bacter. The nitrogen fixation from the atmosphere is such that 

 it cannot be considered as a normal and essential function, 

 necessary to the cell economy of the organism, but rather as an 

 incidental or secondary factor in the cell metabolism. As an 

 addendum to the main bulk of his work Krzmieniewsky men- 

 tions a series of experiments which fail to corroborate the find- 

 ings of Stoklasa, with regard to the formation of by-products, 

 and cast thereby additional doubt on the purity of the cultures 

 of the latter investigator. That this difference in the metab- 

 ohsm (production of organic acids and alcohols) may not be due 

 to differences in the organisms studied or, necessarily, to impuri- 

 ties is shown by some of the data presented by Maze (1902). 



That an organism such as Eurotiopsis gayonii is capable of 

 changing its physiology and the nature of the by-products of its 

 life activities (under anaerobic conditions performing only the 

 process of intramolecular respiration) would tend to convince 

 us that Stoklasa might not have been working with impure cul- 

 tures but may rather have been growing his cultures under con- 

 ditions of anaerobiosis. That such a process of anaerobiosis is 

 possible in Azotobacter may be postulated when we consider the 

 work of Maze on the assimilation of glycerol, lactic acid and 

 aldehyde by Eurotiopsis. 



