290 DARWINISM AND THE PROBLEMS OF LIFE 



the chemical constituents of the organic substance are 

 living albuminoids, the biogens. Now, we know that 

 this substance has a definite form, protoplasm. 



Although the cells may differ widely in form and size, 

 the organs of animals would not be so varied as they are 

 if the cells could not give out different kinds of products. 

 Our skin and viscera consist directly of cells, but they 

 only form the basis of the muscles and bones. 



But, it will be asked, how can the cells create 

 anything new ? 



These elementary units of the organic body feed and 

 grow naturally in virtue of the nourishment circulating 

 in the body. However, they do not need the food 

 solely for their own growth and the maintenance of the 

 vital activity ; from one portion of it they form special 

 substances which they eject at their surface. Thus the 

 skeleton of the articulates was formed as a secretion of 

 the cell-layer of the underlying skin, and our bones and 

 muscles, also, are the secretory products of large numbers 

 of cells. These products have a function ; they serve 

 for support or movement, like the bones and muscles, or 

 for the conducting of stimuli, like the neural substance. 

 On the other hand, the cells that have produced these 

 substances renew and nourish them. 



The great advantage of this kind of organ-construction 

 is in the division of labour, a principle that is also found 

 in civilised life, and forms its foundation. It is at work 

 not only in the body politic, but in every warehouse and 

 factory. This alone makes it possible, for instance, to 

 build a good house ; this can only be done if one part 

 of the workers looks after the building, another the 



