THE HUMAN MECHANISM 5 



coiled springs or lifted weights, and liberate it slowly in the 

 mechanical work of moving the hands of the timepiece over 

 a dial. Still more complex is a locomotive or an automobile, 

 machines in which the power of coal, oil, gasoline, or other 

 fuel or the electricity of a storage battery is applied to swift 

 locomotion. But the most wonderful of all machines is the 

 human body, a complicated piece of apparatus in which the 

 power stored in foods, such as starch, sugar, butter, meat, 

 milk, eggs, and fish, is transformed into that heat by which 

 the body is warmed and into that muscular, nervous, diges- 

 tive, or other work which it performs. 



For delicate and intricate machinery the term " mechan- 

 ism " is often employed, and we may therefore describe 

 the human body either as the " human organism," or the 

 " human machine," or, perhaps best of all, as the HUMAN 



MECHANISM. 



The study or the science of the construction (structure) 

 of this mechanism is called its anatomy; of its ordinary be- 

 havior, operation, or working, its physiology; of its proper 

 management, protection, and care, its hygiene. This textbook 

 is devoted chiefly to an account of its operation and care, 

 that is, to its physiology and hygiene ; but as any true com- 

 prehension of these subjects depends upon some preliminary 

 knowledge of the parts of the mechanism itself, we shall 

 begin by considering briefly the structure or anatomy of the 

 human machine. 



