THE MECHANISM OP LIFE 551 



rather than united, energy is absorbed.^ In the light of this, 

 the fundamental principles of organic transformations of energy 

 follow clearly from the well-known facts of metabolism. There 

 exist in living substance certain compounds possessing strong 

 chemical affinities. Other chemical affinities are introduced from 

 outside into the living cell along with food and oxygen. These 

 relatively simple substances that are introduced are employed for 

 the construction of much more complex compounds, which we have 

 termed living proteids or biogens. In this process the chemical 

 energy that is introduced passes over into the complex compounds in 

 the form of potential energy, and helps to loosen their structure. 

 E.g., it is known that by the introduction of oxygen the biogen 

 molecule takes on an extraordinarily labile constitution, i.e., its 

 intramolecular heat becomes very great. As a result of this the 

 molecule tends toward decomposition, and explodes, partly spon- 

 taneously and partly upon slight external stimulation. This ex- 

 plosive decomposition depends upon a re-arrangement of the atoms, 

 whereby, as in all explosive bodies, within single atomic groups 

 stronger affinities become united than were previously united in 

 the labile molecule. Therefore, as a whole, dissimilatory processes 

 must be associated with a considerable production of energy. The 

 compounds that are derived from this decomposition of the biogens 

 and leave the body, such as carbonic acid, water, etc., contain 

 scarcely perceptible quantities of chemical potential, while the 

 compounds that remain in the body, the residue of the biogens, 

 again possess chemical affinities for food-stuffs and oxygen, and 

 employ them in uniting with the latter. The energy thereby made 

 available is employed again for loosening the biogen molecule, and 

 thus the chain ends. The principle upon which it is based ac- 

 cordingly appears clear : there is a continual storing up of potential 

 chemical energy and a transference of it into other forms ; the 

 source of it is the food and the oxygen ; the original capital is the 

 chemical energy that every minute droplet of living substance has 

 carried over from its ancestors ; and the result is expressed in the 

 work accomplished by the living substance. 



The relations as regards energy that develop in living substance 

 under the influence of stimuli are comprehensible, in their general 

 outlines, upon the basis of these facts. Those cases are simplest in 

 which the stimulus causes an excitation of dissimilation. As has 

 already been seen,^ this process consists of an augmentation of 

 spontaneous processes. The potential energy that is stored in 

 the labile biogen molecules is to a certain extent spontaneously 

 transformed into actual energy, the atoms being rearranged and 

 combined with one another by stronger afiSnities, and an explosive 

 decomposition simultaneously occurring. It is easily comprehen- 

 sible that certain stimuli maj^ increase directly the intramolecular 

 1 Cf. p. 215. ■- Cf. p. 474. 



