306 APPLIED BIOLOGY 



namely, movement, digestion, absorption, respiration, assimi- 

 lation, oxidation, excretion, irritability (simple nervous 

 activity), and reproduction. All these life-processes are 

 within one cell in a paramecium, and require tens of thou- 

 sands of cells in an elephant. But there is a difference in that 

 the paramecium cannot perform any process as well as can 

 a higher animal. In fact, to a large extent a paramecium is 

 doing just what every individual cell in any higher animal 

 is continually doing in carrying on its own life-processes. 



269. Physiological Division of Labor. The fact that the 

 cells in higher animals are specialized to do certain work 

 (e.g., muscle cells to contract or cause movement, stomach- 

 cells to digest, kidney cells to excrete, nerve cells for co- 

 ordination, etc.), is known as physiological division of labor. 

 The advantage of such specialization is shown by an analogy 

 from human society. Each pioneer in the country regions in 

 America had to be his own baker, miller, carpenter, black- 

 smith, cobbler, etc., because special workers in these lines 

 were not near. But such a man never became expert in any 

 of these lines ; he was " a Jack of all trades, master of none/' 

 Nowadays in civilized communities a physiological division of 

 labor has led men to become specialists and learn to do one 

 thing excellently. But there must be a coordination or a 

 working together. One man may specialize as a carpenter ; 

 but he must depend upon other men to be his cobbler, grocer, 

 baker, farmer, and so on through a long list of people who 

 must do things for the one who confines his work to one special 

 line. In our great cities we do not often stop to think of 

 this physiological division of labor which has grown up in 

 our complex human society; but if all the grocers were to 

 close their shops, or as has actually happened, the railroad 

 engineers should stop work and leave us without supplies, 

 then we could realize the complex way in which we have be- 

 come dependent upon other workers in special lines of work. 



All this from human society illustrates the division of labor 



