ENERGY IN BIOLOGY. 115 



much and which are so clear, are of the greatest 

 importance from the practical as well as from the 

 theoretical point of view. 



In the first place, they show us the position and the 

 rank of the phenomena of life in the universe as a 

 whole. They throw fresh light on the noble harmony 

 of the animal and vegetable kingdoms which Priestley, 

 Ingenhousz, Senebier. and the chemical school of the 

 beginning of the nineteenth century discovered, and 

 which was expounded by Dumas with incomparable 

 lucidity and brilliance. Energetics is expressed in a 

 line. "The animal world expends the energy ac- 

 cumulated by the vegetable world." 1 It extends these 

 views beyond the living kingdoms. It shows how the 

 vegetable world itself draws its activity from the 

 energy radiated by the sun, and how animals restore 

 it again, in dissipated heat, to the cosmic medium. 

 It extends the harmony of the two kingdoms to the 

 whole of nature. The new science makes of the 

 whole universe one connected system. 



From a more limited point of view, and so that we 

 may not restrict ourselves to a consideration of the 

 domain of animal physiology, the laws of energetics 

 sum up and explain a multitude of facts and of 

 experimental laws for example, the law of the inter- 

 mittence of physiological activity, the facts of fatigue, 

 the role and the general principles of alimentation, 

 and the conditions of muscular contraction. 



