2 HUMAN PHYSIOLOGY CHAP. 



ferent parts of the body are under our control. We 

 can move the head, hands, feet, and, in fact, the entire 

 body at our pleasure. The bones are moved by the 

 muscles* which are controlled by the nerves that carry 

 the messages sent out by the mind. 



In some respects the body may be compared to a 

 locomotive. The locomotive consists of a furnace, a 

 boiler, a piston, wheels, levers, etc., while the body has 

 bones, muscles, a heart, a stomach, a brain, etc., as its 

 machinery. Coal and wood are put into the furnace, 

 while meats, potatoes, bread, etc., are taken into the 

 stomach, and serve as fuel. The heat from the coal 

 changes the water in the boiler to steam, which is the 

 motive power that turns the wheels and moves the train 

 along the track. The foods taken into the stomach and 

 changed to blood are burned in the cells of the body. 

 The heat thus produced serves to keep us warm and to 

 keep in operation the machinery of the human body. 

 The body differs from the locomotive in that it is self- 

 oiling, self-repairing, and self -increasing in size, some 

 of the foods serving these purposes. Beautiful and 

 wonderful as is the most complicated machine ever in- 

 vented by man, the body exceeds it in beauty of form, 

 delicacy of adjustment, and complexity of organization. 



The study of the human body is one of the most 

 interesting and useful branches taught in our schools. 

 We call this study human anatomy, pJiysiology, and 

 hygiene. 



3. Anatomy. The science which treats of the gross 

 structure of the body, i.e. the shape, size, and location of 



