PART VI. 



THE ENERGY-BALANCE OF THE ORGANISM, 



CHAPTER XXIII. 

 THE ANIMAL BODY AS A MACHINE. 



THE APPLICABILITY OF THE LAW OF THE CONSERVATION OF 

 ENERGY TO LIVING ORGANISMS. 



To all of our not very remote forebears and to the majority of those 

 of our contemporaries who vote, legislate and govern in this our present 

 day, Life was, or is, a thing apart from the Universe, independent of 

 cosmic laws, controlling rather than expressing the forces of nature. 

 The inversion of this primitive idea which was ultimately to result in 

 the attainment of our present conception of life, as the outcome of 

 forces which it does not of itself create, originated in the investigations 

 of that greatest of French chemists, Lavoisier. 



The clue to the true nature of the processes of combustion had 

 previously been provided by the discovery by Priestley that air con- 

 tains a substance which is essential to combustion and is consumed 

 thereby. It was Lavoisier, however, who showed that this gas is 

 absorbed by and becomes combined with the burning substance, and 

 the amplification of this discovery led to the enunciation of the law 

 of the Conservation of Matter. The corresponding law in the domain 

 of energy-transformation was not formulated until 1845, over fifty 

 years later. Nevertheless it is to Lavoisier also that we must accredit 

 the investigations which first established the applicability of the law 

 of the Conservation of Energy to animals. It has frequently happened 

 in the history of scientific investigation, that a truth which was not 

 generally apprehended or clearly enunciated at the time has never- 

 theless been tacitly assumed in advance of their period by investi- 

 gators possessing exceptional powers of insight and discovery. It is a 

 mistake to suppose that successful scientific discovery is the outcome of 

 purely logical processes of thought in the mind of the investigator. 

 The great discoverer appears to be distinguished from equally diligent 

 but less successful investigators quite as much in his possession of a 



