PAET I 



CHAPTER I 

 THE HUMAN MECHANISM 



1. The human body a living organism. The human body, 

 as compared with bodies of water such as lakes and seas, 

 or with heavenly bodies such as the sun, moon, and stars, 

 is a small mass of matter weighing on the average, when 

 fully grown, about 150 Ib. and measuring in length about 

 5 ft. 9 in. It is neither very hot, as is the sun, nor warm 

 in summer and cold in winter, as are many bodies of 

 water, but in life and health has always almost exactly the 

 same moderate temperature, namely, 98.6 F. or 37.5 C. The 

 human body is not homogeneous, that is to say, alike in all 

 its parts, as is the substance of a lake, but consists of very 

 unlike parts eyes, ears, legs, heart, brain, muscles, etc. 

 these parts being known as organs, and the whole body, there- 

 fore, as the human organism. 



The most remarkable peculiarity of the human body, how- 

 ever, is that it is a living organism. A watch has unlike parts 

 spring, dial, hands, case, etc. which are essentially its 

 organs, and the watch might therefore be called an organism; 

 yet it never is so called. We speak of a well-organized army, 

 navy, government, society, church, or school, but never of a 

 well-organized automobile, typewriter, printing press, or loco- 

 motive apparently for the reason that in army, navy, . or 

 school living things play a principal part, while in mere 

 machinery life is wholly wanting. The highest compliment 

 we can pay to a machine is to say that it seems "almost 



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