180 



DIVISION OF LABOR 





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tain functions to perform in conjunction with one another The 

 arm of the human body performs movement. To do this, several 

 tissues, as muscles, nerves, and bones, must act together. A col- 

 lection of tissues performing certain work we call an organ. 



In a simple animal like a sponge, division of labor occurs be- 

 tween the cells; some cells which line the pores leading inward 

 create a current of water, and feed upon the minute organisms 

 which come within reach, other cells build the skeleton of the 

 sponge, and still others become eggs or sperms. In higher animals 



more complicated in struc- 

 ture and in which the 

 tissues are found working 

 together to form organs, 

 division of labor is much 

 more highly specialized. 

 In the human arm, an 

 organ fitted for certain 

 movements, think of the 

 number of tissues and the 

 complicated actions w^hich 

 are f)ossible. The most 



Part of a sponge, showing how cells perform extreme division of labor 



division of labor, ect, ectoderm; 7nes, meso- . • j.u 



derm; emd, endoderm ; c.c, ciliated cells, IS Seen m the Orgamsm 



which take in food by means of their fla- which has the mOSt COm- 

 gellae or large cilia {fla), , , . , » 



plex actions to periorm 

 and whose organs are fitted for such work, for there the cells or 

 tissues which do the particular work do it quickly and very well. 



In our daily life in a town or city we see division of labor between 

 individuals. Such division of labor may occur among other ani- 

 mals, as, for example, bees or ants. But it is seen at its highest 

 in a great city or in a large business or industry. In the stockyards 

 of Chicago, division of labor has resulted in certain men performing 

 but a single movement during their entire day's work, but this 

 movement repeated so many times in a day has resulted in wonder- 

 ful accuracy and speed. Thus division of labor obtains its end. 



Organs and Functions Common to All Animals. — The same 

 general functions performed by a single cell are performed by a 





