PHYSIOLOGY FOR DENTAL STUDENTS 



CHAPTER I. 

 INTRODUCTORY: THE CHEMICAL BASIS OF THE CELL. 



The Scope of Physiology. Physiology is the study of the 

 phenomena of living things, just as anatomy or morphology is a 

 study of their structure. The study of anatomy is most logically 

 pursued by starting with the simplest organisms and gradually 

 proceeding through the more complex forms until man is 

 reached. Except for certain fundamental functions, such as 

 nutrition, which are common to all cells, this method is not 

 the most suitable one to pursue in physiology, because in the low- 

 est organisms all of the functions are crowded together in a lim- 

 ited number of cells indeed, it may be in one single cell. It is 

 easier to study a function when it is performed by a tissue or 

 organ that has been set apart for this particular purpose than 

 when it is performed by cells that do many other things. Another 

 reason for paying more attention to the functions of higher 

 rather than lower animals is that the knowledge which we acquire 

 may be more directly applicable in explaining the functions of 

 man, and therefore in enabling us more readily to detect and 

 rectify any abnormalities. 



During the embryonic development of one of the higher ani- 

 mals, a single cell, the ovum, produces numerous other cells, 

 which become more and more collected into groups, in many of 

 which the cells undergo very marked changes in shape and 

 structure, or produce materials, such as the skeleton or teeth, 

 which show no cell structure whatsoever. Thus we have formed 

 the tissues and organs, each having some particular function of 



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