PART IV 



HUMAN STRUCTURE AND 

 PHYSIOLOGY 



(Chapters XXI to XXVIII, inclusive, by Isabel McCracken) 



CHAPTER XXI 



INTRODUCTION 



The study of physiology and its purpose. — We have 

 found in our study of animals that they are made up of 

 many parts or structures arranged in definite ways. To 

 see many of the parts itiwas necessary to dissect the animals 

 that we have studied most carefully, as the frog and craw- 

 fish. This study of the structure of animals is called the 

 study of anatomy. We must know something of the anat- 

 omy of the animal body to understand what it can do. 



We have learned that each part has its special function 

 and that these various functions constitute the processes 

 which, added together, .are life itself. 



The study of the functions of the various structures of 

 the body is called the study of physiology. 



Since the study of physiology is the study of the parts of 

 the living body in action, the study of human physiology 

 at first hand is very difficult. We can dissect the lower 

 animals easily, and find out at first hand what their parts 

 are and how they are put together, but elementary students 

 cannot dissect the human body. They must depend upon 



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