THE CELL AND ITS STRUCTURE. 25 



saving time by the increased skill of the workman 

 trained to one process alone. This example still holds 

 good as an illustration, but it is quite obsolete as a 

 description of the manufacture of pins, for it is so long 

 ago since pins were made with separate heads, that I 

 can only just remember hoarding up pins of this sort; 

 as occasional curiosities when I was a very small child. 

 Pins are made all in one piece now, which saves the 

 annoyance formerly felt when the head came off some- 

 times just when you wanted it to stay on — a part of 

 the labour which was divided with the owner of the 

 pin by nobody. But the principle is easily under- 

 stood, however antiquated may be the illustration. 

 As the result of the " division of labour " plan 

 adopted among the cells of the animal body, we find 

 cells which are respectively adapted for digesting, 

 for excreting, for feeling, and for moving. When a 

 large number of cells, all having one function, form a 

 large group, we call this group an organ (instrument 

 or machine) ; and an animal ■ that has many different 

 kinds of organs is spoken of as highly organized. 

 But cells, like people, when they do one thing chiefly, 

 learn to do other things badly ; and the cell that is 

 adapted for digesting, for instance, almost forgets how 

 to feel, or to move, while the cell that is specially 

 adapted for feeling almost forgets how to move, and 

 so on. 



Thus there are groups of digesting cells, forming 

 gastric and other glands ; groups of excreting cells, 

 called kidneys ; groups of cells that provide foi- the 



