144 Evolution of Life and Form. 



changing shape without disintegration. Matter also 

 gains that which science speaks of as elasticity. Now 

 what is elasticity ? Not, as people generally think 

 the mere power of elongation, calling a thing elas- 

 tic that can be pnlled out like a piece of India- 

 rubber. An elastic body in the popular sense 

 is not an elastic body from the scientific point of 

 view, and, strange as it may sound, glass is much 

 more elastic than India-rubber. Yet the glass does 

 not elongate and is brittle. The proper definition 

 of elasticity is the power of recovering the original 

 form after distortion, and matter gradually acquires 

 this power. As life develops, the equilibrium of 

 the compounds that make up the form becomes 

 more and more unstable, while at the same time the 

 general cohesion of the form increases ; when we 

 come to the higher forms, such as the body of man, 

 we find a power of maintaining the central position 

 greater than we find in any other form, together 

 with an increased plasticity and elasticity ; so that a 

 man can adapt himself to the cold of the polar re- 

 gions, and to the heat of the tropics and of the equa- 

 torial zone, without losing his body, in a way 

 that no lower animal can match, that is, he has 

 the power of adapting his physical body to surround- 

 ing conditions to a greater extent than is the case 

 with any other form. Coming back to the mineral 



