PHYSIOLOGY AND ANATOMY 



I. WHAT THE STUDY OF PHYSIOLOGY MEANS. 



From our earliest days we are familiar with living 

 forms. We know that each living form must perform cer- 

 tain actions every day in order to live; but few of us have 

 a clear idea of why these actions maintain life, or of the 

 part each separate action plaj'^s in keeping us aUve. For 

 example, if asked why we eat, we answer, " To keep us 

 alive," but that answer does not explain how food gives 

 life. Again, we see gardeners watering plants, repotting 

 them in new earth, taking care to place them in sunlight, 

 and we recognize that all these actions are necessary to 

 the life of the plants. We know that dogs and cats, horses 

 and cows, must be fed and cared for to keep them alive 

 and healthy. In fine, we know that to maintain life all 

 living bodies, whether plant or animal, must repeat certain 

 actions continually, or else die ; but we do not know how 

 these actions produce life. It is this question of " how " 

 and " why " that the present study of Physiology is to 

 answer. 



Method of study. — How shall we begin the study? 

 An example wiU indicate the method. If we see a man 

 moving the handle of a certain machine up and doM'n and 

 see a stream of water issuing from another part of the 

 same machine, we know at once that the movement of 

 the handle in some way causes the flow of water. In 



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