24 THE FITNESS OF THE ENVIRONMENT 



to preserve, an ideal form, while through 

 them flows a steady stream of energy and mat- 

 ter which is ever changing, yet momentarily 

 molded by life; organized, in short. This 

 idea, to which we must later return, could 

 not possess in the early nineteenth century 

 the significance and value which now attach 

 to it. It needed the explanation which the 

 study of metabolism has at length provided. 



A 



METABOLISM 



Metabolism is the term applied to the in- 

 flow and outflow of matter and energy and 

 their intermediary transformations within the 

 organism. Its serious investigation began 

 with Lavoisier, the principal founder of mod- 

 cation et a ce mouvement perpetuel, qui rendent si difficile 

 Papplication des sciences generates. " (" Rapport," p. 150, etc.) 

 " Dans les corps vivans chaque partie a sa composition propre 

 et distincte; aucune de leurs molecules ne reste en place; 

 toutes entrent et sortent successivement : la vie est un tour- 

 billon continuel, dont la direction, toute compliquee qu'elle, 

 est, demeure constante, ainsi que l'espece des molecules qui 

 y sont entrainees, mais non les molecules individuelles elles- 

 memes. . . . Ainsi la forme de ces corps leur est plus 

 essentielle que leur matiere," etc. (Ibid. p. 200.) — " Eloges 

 historiques," Vol. I, p. 200. Quoted by Merz, "A History of 

 European Thought in the Nineteenth Century," Vol. I, p. 

 129. Edinburgh and London, 1898. 



