THE HUMAN MACHINE 



2r,7 



in groups as tissues and organs that make the complicated actions 

 of man possible. Division of labor has arisen because of the 

 complex needs and work of the organism. 



The Human Body a Machine. — In all animals, and the human 

 animal is no exception, the body has been likened to a macliine 

 in that it turns over the latent or potential 

 energy stored up in food into kinetic 

 energy (mechanical work and heat), 

 which is manifested when we perform 

 work. One great difference exists be- 

 tween an engine and the human body. 

 The engine uses fuel unlike the substance 

 out of which it is made. The human 

 body, on the other hand, uses for fuel 

 the same substances out of which it is 

 formed ; it may, indeed, use part of its 

 own substance for food. It must as well 

 do more than purely mechanical work. 

 The human organism must be so deli- 

 cately adjusted to its surroundings that 

 it will react in a ready manner to stimuli 

 from without ; it must be able to utilize 

 its fuel (food) in the most economical 

 manner ; it must be fitted with machinery 

 for transforming the energy received from 

 food into various kinds of work ; it must 

 properly provide the machine with oxygen 



so that the fuel will be oxidized, and the The human body seen from 



products of oxidation must be carried the side in iongitudin:U 



section. 



away, as well as other waste materials 



which might harm the effectiveness of the machine. Most 



important of all, the human machine must be able to repair 



itself. 



In order to understand better this complicated machine, the 

 human body, let us briefly examine the structure of its parts 

 and thus get a better idea of the interrelation of these parts and 

 of their functions. 



