48 THE CONTROL OF LIFE 



before our eyes ; so is the complex of external influences 

 which we call the environment ; function is a general 

 term for the actions and reactions between them, and 

 for the internal activities such as the beating of the 

 heart and thinking which go on without obvious stimula- 

 tion from outside. Sometimes the organism acts on 

 its surroundings in a masterly way, as when beavers 

 cut down trees and build dams ; or when a sheep devours 

 part of its environment, namely, the grass ; or when a 

 lichen eats into the surface of the rock. This might 

 be represented by the formula, as Professor Patrick 

 Geddes suggests, -> / -> e. At other times the environ- 

 ment seems to get the upper hand, impressing changes 

 upon the organism, inciting it by warmth to more rapid 

 change or slowing down by cold the vital processes, 

 now inducing change of colour and again effecting deeper 

 dints. This might be represented by the formula 

 -E ■> / -> ; and thus we reach Professor Geddes's 

 useful idea, that living is a continual adjustment of a 



twofold dynamic relation : { =. In a dry 



•^ <- f <- E ^ 



seed that has been lying for several seasons in the 

 granary, in a desiccated paste-eel that has remained 

 in a state of latent life for years, the twofold dynamic 

 relation has stopped altogether or is so near interruption 

 that no evidence of its persistence can be found. But the 

 organisation that makes living possible has not dis- 

 appeared, as is easily proved by planting the hard seed 

 in the ground or by surrounding the brittle paste-eel 

 with water. 



