THE HUMAN MACHINE 



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Tissues build organs. 



for example, the hand. It is made up of skin, bones, 

 muscles, nerves, and other tissues. But these tissues 



all work together. 

 We call such groups 

 of tissues an organ 

 and the different 

 plants and animals 

 are called organisms 

 because they are 

 made up of numer- 

 ous organs. 



The Human Machine an Organism. In man, the most 

 complicated of all machines, we find many systems of 

 organs. We find the protective covering or skin, beneath 

 it a layer of fat, then muscles giving form to the body and 

 by attachment to the bones allowing movement. We 

 also find a tube running through the body, made up of 

 many kinds of cells, and varying greatly in structure. 

 Since it has a general work to do, we speak of it as the 

 digestive tract, for its job is to make food usable in the 

 body by digestion. Other systems of organs are found. 

 We know the use of the lungs in breathing and of the heart 

 in pumping the blood over the body. Most wonderful of 

 all is the directive apparatus called the nervous system. 

 By this complicated group of organs, those of sight, hear- 

 ing, smelling, tasting, and touching, we are able to know 

 about things which surround us. And by means of the 

 nerves, which connect these organs of sensation with the 

 directive apparatus called the brain, our human machine 

 is able to run intelligently. 



SELF-TESTING EXERCISE 



Select from the following list those words which best fill the blank spaces 

 in the sentences below and arrange the words in proper numerical order. 

 A word may be used more than once. 



