CHAPTER II 



A STUDY OF PHYSICAL FORCES INVOLVED IN BIOLOGICAL 



ACTIVITIES* 



INTRODUCTION 



It is becoming more and more evident that besides the chemical 

 components and forces which constitute the mechanism and activities 

 of the cell and which will be treated in the next chapter, there are 

 certain physical forces and conditions as important and very depen- 

 dently related which are operative. In the physical or chemical ap- 

 proach to physiology the writers do not assume the role of being 

 chemists or physicists and they write somewhat hesitatingly and reluc- 

 tantly upon such matters, yet the stream separating the various 

 branches of science must be spanned. The purpose, as writers, will be, 

 therefore, to bring the elementary gist of the physical laws and phenom- 

 ena, which bear upon microbial physiology, to the attention of the 

 student for memory-helpfulness and suggestiveness. Should greater 

 knowledge or more extensive reading be desired the student is asked to 

 consult the literature appended at the end of this chapter. 



ENERGY 



Energy may be most effectively presented in the general law 

 through which it defines itself and governs applications, and in the 

 specific expressions in applications which provide the detailed back- 

 ground. Energy is work or capacity to perform work. This is found 

 in all living units. Work is going on. Whether this energy is desig- 

 nated as mechanical, thermal, electrical, chemical makes no particular 

 differences for the form is only one aspect of it. 



Energy may be transformed from thermal into electrical or chemical 

 into thermal; in fact "all forms of energy are convertible. The total 

 energy of any substance or system cannot be altered by the mutual 

 actions of its parts." Furthermore, energy is practically indestructible. 



* Prepared by Charles E. Marshall and Arao Itano. 



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