244 PHYSIOLOGY OF BACTERIA 



seems to disagree with the finding of Abderhalden and 

 Rona (1905) that the protein of Aspergillus niger was 

 the same regardless of the source of nitrogen. Terroine, 

 Wurmser and Montane (1922), working with the same 

 mold, found little difference in the nitrogen content of 

 the mycelium when the source of nitrogen was ammonium 

 sulfate, peptone, urea, or sodium nitrate; but it dropped 

 decidedly with guanidine. Perhaps it is the proportion 

 of the different kinds of proteins within the cell which 

 brings about the differences in different yeasts. 



A well-known illustration of the influence of the kind 

 of food upon the final amount of growth is the appearance 

 of pinpoint colonies on agar. Many milk streptococci 

 give such colonies on standard, i.e., sugar-free agar, 

 while the colonies on glucose agar are of normal size. 



SUMMARY 



The final number of cells which can develop in a 

 given volume of medium depends to a large extent upon 

 the chemical composition of the food. With different 

 types of material for cell construction, yeast will produce 

 not only different quantities of cells, but also cells of 

 considerable variation of physiological characters. 



(c) ENDPOINTS WITH AN ABUNDANCE OF FOOD 



In all these experiments, the source of energy was used 

 completely; the nitrogenous building material was used 

 almost completely (see Exp. 22-23 of Table 65). It is 

 generally taken for granted that a poorer food, even 

 if given in abundance, will produce a smaller crop. The 

 facts seem to bear out the assumption. 



Really, the situation is not as simple as it seems at first glance. 

 Our easy acceptance of the facts is probably based upon an analogy 

 (perhaps subconsciously) with higher organisms. A poor soil will 



