MODERN EVOLUTION. 



225 



— which is the special work of the nervous system. 

 It was an old Greek maxim that " a man may once 

 say a thing as he would have said it: he cannot say 

 it twice." This is the warrant for transferring a few 

 sentences on the origin of the nerves from my Story 

 of Creation. They are but a meagre abstract of Mr. 

 Spencer's long, but luminous exposition of the sub- 

 ject. 



" As every part of an organism is made up of 

 cells, and as the functions govern the form of the 

 cells, the origin of nerves must be due to a modifica- 

 tion in cell shape and arrangement, whereby certain 

 tracts or fibres of communication between the body 

 and its surroundings are established. 



" But what excited that modification? The all- 

 surrounding medium, without which no life had 

 been, which determined its limits, and touches it at 

 every point with its throbs and vibrations. In the 

 beginnings of a primitive layer or skin manifested 

 by creatures a stage above the lowest, unlikenesses 

 would arise, and certain parts, by reason of their 

 finer structure, would be the more readily stimulated 

 by, and the more quickly responsive to, the ceaseless 

 action of the surroundings, the result being that 

 an extra sensitiveness along the lines of least re- 

 sistance would be set up in those more delicate 

 parts. These, developing, like all things else, by use, 

 would become more and more the selected paths of 

 the impulses, leading, as the molecular waves thrilled 

 them, to structural changes or modification into 



