14 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



experiment, and the difference from the theoretical 

 result is less than the errors of the experiment. We may 

 conclude then that all energy processes occurring in the 

 organism are conservative ones. 



But does the second law also apply? It is imme- 

 diately evident that it does not apply in all the strictness 

 that we can see in inorganic processes for the fraction of 

 energy degraded is always very much less than in a 

 purely physical process : a fact which we express hy 

 saying that the organism, considered as a machine, is 

 very much more economical than any physico-chemical 

 mechanism that we can construct. A comparison 

 between an electric glow lamp and a phosphorescent 

 organism brings out this contrast very clearly, for in the 

 latter chemical energy is transformed into light without 

 first of all passing into the form of heat. Shall we 

 conclude, then, that the law of energy dissipation does 

 not apply to the organism? If we consider only the 

 highly specialised metabolism of the warm-blooded 

 animal we receive little support for this conclusion for 

 this metabolism is that of the type of a heat-engine. 

 Certain food-stuffs, carbohydrates, fats and proteids, 

 substances of high chemical potential — or high energy 

 value — are ingested and undergo transformation into 

 carbon dioxide, water and urea, that is into substances 

 of low chemical potential or low energy value. The 

 energy difference is represented partly by the work done 

 by the animal, and partly by the heat radiated off and 

 contained in the egesta. That is to say the changes are 

 just those of a Carnot cycle, energy being drawn from a 

 source of high potential and passing into an energy sink 

 at low potential. Energy is dissipated during the cycle, 

 but the amount so degraded is very much less than in the 

 heat-engine. Now the metabolism of the warm-blooded 



