THE ENERGY CONCEPT OF LIFE 15 



Actions and reactions refer chiefly to what is going on be- 

 tween the parts of the organism in chemical or physical con- 

 tact, and are subject to the two dynamical principles referred 

 to above. Interactions, on the other hand, refer to what is 

 going on between material parts which are connected with 

 each other by other parts, and cannot be analyzed at all by the 

 two great dynamical principles alone without a knowledge of 

 the structure which connects the interacting parts. For ex- 

 ample, in interaction between distant bodies the cause may be 

 very feeble, yet the potential or stored energy which may be 

 liberated at a distant point may be tremendous. Action and 

 reaction are chiefly simultaneous, whereas interaction connects 

 actions and reactions which are not simultaneous; to use a 

 simple illustration: when one pulls at the reins the horse feels 

 it a little later than the moment at which the reins are pulled 

 — there is interaction between the hand and the horse's mouth, 

 the reins being the interacting part. An interacting nerve- 

 impulse starting from a microscopic cell in the brain may give 

 rise to a powerful muscular action and reaction at some distant 

 point. An interacting enzyme, hormone, or other chemical 

 messenger circulating in the blood may profoundly modify the 

 growth of a great organism. 



Out of these physicochemical principles has arisen the con- 

 ception of a living organism as composed of an incessant series 

 of actions and reactions operating under the dynamical laws 

 which govern the transfer and transformation of energy. 



The central theory which is developed in our speculation 

 on the Origin of Life is that every physicochemical action and 

 reaction concerned in the transformation, conservation, and 

 dissipation of energy, produces also, either as a direct result or 

 as a by-product, a physicochemical agent of interaction which 

 permeates and afects the organism as a whole or afects only some 



