4 PHYSIOLOGY OF BACTERIA 



defined compounds only; (3) the control of the concentra- 

 tion of food; (4) the complete analysis of all metabolic 

 products; (5) the circumstance that all experiments are 

 averages of millions or billions of individual cells which 

 are all of the same kind and the same age; (6) the very 

 rapid rate of growth; (7) the possibility of separating to a 

 considerable extent the food for energy supply from the 

 food needed for building material. 



There is one disadvantage in all experiments with 

 lower fungi, i.e. their minute size. (A general concep- 

 tion of the meaning of the size of microorganisms can be 

 obtained from Table 132 of the ' ' Appendix.'') This small 

 size makes the determination of the ''crop" diffi- 

 cult, especially with bacteria, while with molds and 

 yeasts, it is fairly easily accomplished. But even with 

 bacteria, direct and indirect methods have been devised 

 which will be found in the chapter on Growth. 



Not only from the viewpoint of general physiology 

 is the physiology of microorganisms important; it is also 

 of great value in applied bacteriology. There can be no 

 doubt that future developments in the latter field will 

 depend to a large extent upon a better understanding of 

 the physiology of microorganisms. The canning indus- 

 try, as well as chemical and physical disinfection, need 

 urgently a deeper knowledge of the laws of death of 

 bacteria, while the fermentation industries require more 

 detailed information regarding the different types of fer- 

 mentations, and of the factors influencing them; the bread 

 yeast industry is likewise interested in further advances in 

 the studies of growth and nutrition of microorganisms. 



(6) PARTIAL FUNCTIONS 



Primitive Functions. — The only way we can study the 

 mechanism of life is to separate life into a number of 



