96 LIFE AND DEATH. 



seen with respect to heat and motion is to some 

 degree true of all other forms of energy, as Lord 

 Kelvin has shown. The principle of the degradation 

 of energy is very general. Every manifestation of 

 nature is an energetic transformation. In each of 

 these transformations there is a degradation of energy — 

 i.e., a certain fraction is lowered and becomes less 

 easily transformable. So that the energy of the 

 universe is more and more degraded; the higher 

 forms are lowered to the thermal form, the latter 

 increasing at temperatures which become more and 

 more uniform. The end of the universe, from this 

 point of view, would then be unity of (thermal) energy 

 in uniformity of temperature. 



Importance of the Idea of Energy in Physiology. — 

 I have said that the application of Carnot's principle 

 furnished numerical relations between the different 

 energetic transformations. 



The science of living beings has not yet reached 

 that point of development at which it is possible for 

 us to obtain its numerical relations. However, the 

 consideration of energy and the principle of conserva- 

 tion has altered the outlook of physiology on many 

 questions which are of the highest importance. 



The determination of the sources from which plants 

 and animals draw their vital energies; the mediate 

 transformation of chemical energy into animal heat in 

 nutrition, or into motion in muscular contraction ; the 

 chemical evolution of foods ; the study of soluble 

 ferments — all these questions are of considerable 

 importance when we wish to understand the 

 mechanisms of life. They are therefore depart- 

 ments of physiological energetics in which great 

 advances have already been made. 



