ADAPTATION TO ENVIRONMENT 23 



curely and augment the mound, while others fall at 

 random and roll away, the desired result being achieved, 

 however a memorial to the one who lies beneath 

 the pile. If the result of man's haphazard assemblage 

 of organs is to some extent adequate to the needs of 

 his present environment, it is because during the age- 

 long processes of evolution all the fatally awkward 

 combinations have been eliminated by a struggle so 

 keen that the slightest variation in the length of a 

 leaf, the strength of a limb or the color of an egg, 

 has given the victory to a rival species. Through- 

 out this struggle survival has depended on one of 

 two conditions : the possession of extreme stability, 

 the quality of withstanding all destructive forces in 

 the environment ; or the possession of lability, the 

 quality of adaptability to various conditions in the 

 environment. Rocks are an example of the first 

 condition ; man and higher animals of the second. 



Twenty-four hundred years ago Heraclitus likened 

 life to a flame, and no analogy more fitting has ever 

 been proposed. Life is sustained by the same sort of 

 combustion as that in the flame. The contour of the 

 flame, like the outward aspect of the body, is ever the 

 same, but the contents of both are continually chang- 

 ing. In the flame atoms of carbon and of oxygen are 

 constantly combined to form carbon dioxid and energy 

 is constantly released in the form of heat, while in the 

 body energy is derived from the oxidation of carbon 

 contained in foodstuffs . Like the energy in coal the 

 energy latent in food compounds was obtained origi- 

 nally from the sun. The energy-containing food com- 

 pounds in plants are devoured by plant-eating animals, 



