CHAPTER XV 

 FOOD 



77. The Human Body a Machine. The human body 

 has certain characteristics similar to those of a locomotive 

 or engine. It needs fuel from which to obtain energy 

 for movement. This fuel must be oxidized to produce 

 heat, which is transformed into muscular energy and 

 enables the body to move about as the individual desires. 

 The locomotive has in it fire from which the heat is 

 transmitted to the water in the boiler. The water is 

 changed into steam, the steam under the control of the 

 engineer is allowed to pass to the cylinders and drives the 

 piston back and forth by the energy which it received 

 from the fire, and thus the heat energy of the steam is 

 transformed into mechanical energy. The wheels of 

 the locomotive are made to turn and the whole machine 

 moves along the track. 



The engineer in the cab of the locomotive corresponds 

 to the brain in the human body. The engineer controls 

 the locomotive by controlling the steam. The brain 

 controls the energy in the human body by controlling 

 the production of heat energy, its use, and its escape 

 from the body. The locomotive, however, must have 

 persons in charge of it and a continual supply of fuel to 

 make it a machine by which work can be done. The 

 human body needs a continuous supply of fuel, which is 

 taken in the form commonly called food, but it does not 



