366 AUGUSTO BONAZZI 



The difference between the action of phosphates on zymase 

 action and of the nitrates on cell metaboHsm lies in the fact 

 that the nitrate proves to be actually organized by the cells 

 whereas the phosphate in the work of Harden and Young is 

 merely provisionally tied in an undisturbed form. 



That this difference might be due to the fact that in the one 

 case we are deaUng with a "figurated" ferment while in the other 

 we are only in presence of specific enzyme is not to be overlooked 

 and investigation along this hne may prove to us the possibihty 

 of this line of reasoning. In fact, the locaUzation of the organ- 

 ized nitrogen in the Azotobacter cultures might be intracellular 

 as well as extracellular and studies on this point would enhance 

 our knowledge of the physiology of the organism concerned. 

 Such studies are now under way in this laboratory. 



In the second or maintenance phase, such complexes appear 

 to be reworked, partially burned, partially utiUzed in the build- 

 ing of cellular substance and partially secreted in the surround- 

 ing medium in the form of soluble by-products. During this 

 phase the nitrogen is actually assimilated, directly contrary to 

 the belief of Hills. 



A loss of nitrogen appears to take place during the first phase, 

 a loss which, if shght, may be again made up in the second phase 

 of development. The complication brought about by this first 

 phase in the interpretation of the results does not render the 

 term ''ferment power" valueless or render useless the meaning 

 adopted by Duclaux for this term but is only an example of 

 what should be expected when studying the physiology of bac- 

 teria. Examples of a similar nature are not wanting in other 

 branches of science and mention need only be made here of the 

 limited value of the respiratory quotient in the study of the 

 physiology of the Crassulaceae among plants and of Ascaris and 

 Lumbricus among animals. 



In concluding a word may be said of the practical interpre- 

 tations of the above findings. 



The activity of Azotobacter as a fixer of atmospheric nitrogen 

 in the field is not easily demonstrated. Actual gains due to this 

 organism in the nitrogen contents of a soil in the field are seldom 



