IX.] THE DYNAMICS OF LIFE. 95 



energy which is liberated in the combustion of the fuel 

 that is burned in the furnace during that time. But if 

 the steam-engine works in connexion with one of Arm- 

 strong's hydraulic accumulators/ energy, or motive power, 

 is stored in the accumulator ; so that work may continue 

 to be done for some time after the steam is turned off or 

 the fire put out. The question I have asked is this: 

 Does the animal organism resemble the steam-engine 

 working without an accumulator, which can only transform 

 the motive power which is at that very instant liberated in 

 the chemical process of combustion ? Or does it rather 

 resemble the steam-engine working with an accumulator, 

 which stores motive power in a form that can be drawn on 

 when wanted ? 



I believe there is conclusive evidence that the latter is Vital 

 the fact. I believe there is conclusive evidence that the ®'^*^''sy- 

 living animal contains a variable quantity of a peculiar 

 form of static actual energy, which is capable of being 

 transformed when needed either into heat or into muscular 

 motive power. I propose to call this vital energy ; ^ 

 and I regard it as a distinct form of actual energy, just 

 like heat, electricity, magnetism, or the energy of motion. 

 An animal, regarded as a motor apparatus, may thus be 

 compared to a steam-engine doing work with the assist- 

 ance of an accumulator. In both, energy is being con- 

 stantly obtained by the combustion of carbon (for the 

 oxidation that goes on in the lungs and throughout the 

 body is combustion, differing from that of a furnace only 

 in being slower) ; in both, the energy, when not at the 

 moment wanted to do work, passes into the static form. 

 In the steam-engine it passes into the static potential 

 energy due to the raised weight of the accumulator ; in 

 the animal, into that form of static actual energy which 

 I propose to call vital energy. And in both, it is capable 

 of being used as motive power when wanted to do work. 



1 P. 21. 



2 It -will be jiei'ceived that vital energij is by no means a synonymous 

 expression with the vital principle. If what I have endeavoui'ed to 

 establish on the subject of vital energy is proved to demonstration, it still 

 leaves the mystery of the vital principle exactly where it was before. 



