112 IRRITABILITY 



decreases. Above all it would seem to me to be in the interest 

 of the preservation of the organism and especially of those parts 

 in which there is a high energy production and particularly those 

 substances in which energy production predominates, that the 

 material necessary for its formation is always at its disposal in 

 sufficient quantity. Otherwise the capability of action of the 

 organism would be impaired at every moment or at least suffer 

 great fluctuations. 



In accordance with this we must suppose that under physiologi- 

 cal conditions all those substances required to replace the disin- 

 tegrated molecules are always present in the cell in sufficient 

 quantity and suitable form to replace at once those lost by exci- 

 tation. Further, without doubt, in the organism which is always 

 aerobic, oxygen must be present in certain quantities to assure at 

 any moment oxygen replacement following oxydative disinte- 

 gration, to guarantee sufficient amount for succeeding stimulation. 



A further question arises: How is it that the material lost 

 in disintegration is always replaced in just sufficient quantity 

 to establish the metabolic equilibrium? In short, how are we 

 to understand in a mechanical sense the self-regulation of 

 metabolism ? 



In the preservation of metabolic equilibrium, we have a pro- 

 cess before us, the principle of which is nowadays restricted to 

 living substance. In my "Biogen hypothesis,"^ I have associated 

 the self -regulation of metabolism with the chemical equilibrium 

 in interreacting masses. I have considered the metabolic self- 

 regulation as the expression of the formation of a mass equilib- 

 rium between the quantity of foodstuffs and the quantity of a 

 hypothetical combination of living substance, the biogen, which 

 continuously disintegrates and builds up again of its own accord. 

 In fact, however, we have in the chemical equilibrium of reacting 

 mixtures in the non-living world, a principle which is completely 

 analogous to the self-regulation in living substance. The chemical 

 facts are, indeed, well known. If we take the classical example 

 of the formation of ethylacetat from acetic acid and alcohol, 



1 Ma:c Verworn: "Die Biogenhypothese." Jena 1903. Compare also Max Verworn: 

 Allgemeine Physiologic V. Aufl. Jena 1909. 



