2 STUD JE^ IN PHYSIOLOGY 



nation of the force exerted by the steam. In other words, 

 the scientific student of an engine would necessarily study 

 physics and chemistry, the sciences that lead to the solution 

 of the problems just suggested. 



And finally, if we wished to become competent engineers, 

 we should seek to acquire also the practical knowledge of 

 how to get the most work out of a locomotive. We should 

 study the best methods of feeding in the coal and of 

 regulating the supply of water and of air; we should 

 determine the amount of oil required, and the length of 

 time the engine would run before needing a rest. 



Let us now summarize what we have learned thus far. 

 An engine may be considered in at least three different 

 ways. We may look at it as a collection of various pieces 

 of iron and brass, and may devote our time to studying the 

 form of the parts and the way they are put together. By 

 watching the change of water into steam, and again by ob- 

 serving the movement of wheels and levers, we may learn the 

 uses of the parts. Or finally, we may study the machine 

 with a view of determining the most successful methods of 

 keeping it in good running order. 



The Study of the Human Body. The human body, too, is 

 a machine. But it is far more complicated than any loco- 

 motive and capable of doing many more kinds of work. 

 The body not only can move about and carry things from 

 place to place, but it can also grow and repair itself, and 

 within the body the mind can feel and think. Like the 

 engine, however, it can be studied in three different ways. 

 We may discuss its structure, its activities, and its proper 

 care. When we are considering animal machines, these 

 three branches of study are known respectively as a-nat'o-my, 

 phys-i-ol'o-gy, and Jiy'gi-ene. 



Anatomy. By the anatomy of an animal is meant the 

 study of its structure. If one is considering the anatomy of 

 the human body, for instance, one may discuss the form of 

 the several parts, their microscopic structure, their positions 



