ENERGY IN BIOLOGY. 103 



a chemical phenomenon which always precedes them, 

 and a thermal phenomenon which always follows 

 them. They are lost sight of, as it were, between 

 manifestations which strike our attention. Generally 

 speaking, intermediary energies often escape us 

 even in physics. Only the extreme manifestations 

 are clearly seen. In the presence of the organism 

 we are, as it were, in electric lighting works which 

 are run by a fall of water, and at first we only 

 see the mechanical energy of the falling water, 

 of the turbine and dynamo at work, and the 

 photic energy of the lamps which give the light. 

 Electrical energy, an intermediary, which has only 

 a transient existence, does not impose itself on our 

 attention. 



And so vital energies for this twofold reason, in- 

 trinsic and extrinsic, are not readily apparent To 

 reveal them, the careful analysis of the physiologists 

 is required. They are acts, in most cases silent and 

 invisible, which we should scarcely recognize but by 

 their effects, after they have terminated in familiar, 

 phenomenal forms. This is, for example, what goes 

 on in the muscle in process of shortening, in the nerve 

 carrying the nervous influx, in the secreting gland. 

 And this is what constitutes the different forms of 

 energy which w r e call vital properties. M. Chauveau 

 and M. Laulanie use the phrase physiological u'ork 

 to distinguish them. Vital energy would be prefer- 

 able. It better expresses the analogy of this special 

 form with the other forms of universal energy; it 

 helps us better to understand that we must hence- 

 forth consider it as exchangeable by means of 

 equivalents with the energies of the physical world 

 just as they are exchangeable one with another. 



8 



