INTRODUCTION 



THE science which treats of the structure, function and 

 organization of living forms, both vegetable and animal, is 

 called biology. That branch of biology which describes ani- 

 mal life exclusively is termed zoology, while that branch 

 which describes vegetable life exclusively is termed botany. 



The study of the form of organisms, both vegetable and 

 animal, is termed morphology. Morphology is further di- 

 vided into ( i ) histology, which treats of the formed elemen- 

 tary constituents of organisms, and (2) anatomy, which 

 treats of the parts and organs of the organism. 



After the form and structure of an organism has been 

 studied, the next step is the study of the work which the or- 

 ganism has to perform. This study of the vital phenomena, 

 or life, of the organism is called physiology. Physiology 

 may be either animal or vegetable. Human physiology is 

 that branch of physiology which treats of the vital phenom- 

 ena occurring in man. 



The structural unit of the body is the cell. Myriads of 

 cells are grouped together to form organs. An organ may be 

 defined as a group of cells combined together to perform 

 some special function, e. g., the kidney is an organ whose 

 special function is the secretion of urine. The organs are 

 further grouped together to form systems. Thus we have 

 the circulatory system composed of the heart, arteries, veins, 

 and capillaries. Now the study of the function which the 

 circulatory system has to perform is the physiology of circu- 

 lation. Likewise we may subdivide physiology into the phy- 



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