STUDIES ON AZOTOBACTER CHROOCOCCUM BEIJ. 353 



development in a culture there is a greater transformation of 

 the crude food substances than during the later stages, a con- 

 clusion that is corroborated by the opinion expressed in the 

 previous pages. 



We see thus: 1, that the term ^^ ferment power" should not be 

 considered as a function, constant throughout the life cycle of 

 Azotobacter and, 2, that an organism such as this is capable of 

 utilizing the carbohydrate of a culture in a process of ''storage" 

 or transformation without a corresponding cellular development. 



General considerations on carbon relations 



In the preceding pages we have assumed that that quantity of 

 sugar carbon as such which disappears from the solution is to 

 be found in the cells and their by-products. That it is not to be 

 found in the cells themselves is shown by the high coefficient of 

 "ferment power" in a young culture of the organism in question, 

 since this value is based on that quantity of sugar that is ''con- 

 sumed" by the unit of cell substance in the unit of time. 



Objection could be raised to the conception "unit of cell sub- 

 stance" only on the basis of numbers of active cells since the law 

 of multiplication, when all factors remain equal during the dura- 

 tion of the experiment, makes the number of cells found at the 

 end of an incubation period equal to the number that has been 

 active throughout this period, provided the number of cells at 

 the beginning is considered as unity.^ 



Nevertheless the final weight of cellular dry matter in a cul- 

 ture represents the algebraic summation of the two opposite 

 phenomena of anabolism and catabolism, a value related not 

 only to the size of the inoculum itself, but also to the activity of 

 the organism concerned. 



In other words, it furnishes an index both of the "growth 

 capacity" of the organism and its ability to build living bacterial 

 substance, as well as of its actual capacity as a ferment. 



^ Expressed in terms of equation: N = n — 1 where A'^ is the number of units 

 at the end and ?i is the number of units actually active during the whole period 

 of incubation, each unit of the same number of cells as the original inoculum 

 which has multiplied in geometrical proportion on incubation. 



