I] OF EVOLUTION AND ENTROPY 11 



world*. He may even find a certain analogy between the slow, 

 reluctant extension of physical laws to vital phenomena and the slow 

 triumphant demonstration by Tycho Brahe, Copernicus, GaHleo and 

 Newton (all in opposition to the Aristotelian cosmogony), that the 

 heavens are formed of like substance with the earth, and that the 

 movements of both are subject to the selfsame laws. 



Organic evolution has its physical analogue in the universal law 

 that the world tends, in all its parts and particles, to pass from 

 certain less probable to certain more probable configurations or 

 states. This is the second law of thermodynamics. It has been 

 called the law of evolution of the world'f ; and we call it, after Clausius, 

 the Principle of Entropy, which is a literal translation of Evolution 

 into Greek. 



The introduction of mathematical concepts into natural' science 

 has seemed to many men no mere stumbling-block, but a very 

 parting of the ways. Bichat was a man of genius, who did immense 

 service to philosophical anatomy, but, like Pascal, he utterly refused 

 to bring physics or mathematics into biology: " On calcule le retour 

 d'un comete, les resistances d'un fluide parcourant un canal inerte, 

 la Vitesse d'un projectile, etc.; mais calculer avec BorelU la force 

 d'un muscle, avec Keil la vitesse du sang, avec Jurine, Lavoisier et 

 d'autres la quantite d'air entrant dans le poumon, c'est batir sur un 

 sable mouvant un edifice sohde par lui-meme, mais qui tombe bientot 

 faute de base assureej." Comte went further still, and said that 

 every attempt to introduce mathematics into chemistry must be 

 deemed profoundly irrational, and contrary to the whole spirit of 

 the science §. But the great makers of modern science have all gone 

 the other way. Von Baer, using a bold metaphor, thought that it 

 might become possible " die bildenden Krafte des thierischen Korpers 

 . auf die allgemeinen Krafte oder Lebenserscheinun^en des Weltganzes 

 zuriickzufiihrenll." Thomas Young shewed, as BorelU had done, 

 how physics may subserve anatomy; he learned from the heart and 

 a,rteries that " the mechanical motions which take place in an animal's 

 body are regulated by the same general laws as the motions of 



* So said Lobatchevsky. 



t Cf. Chwolson, Lehrbuch, iii, p. 499, 1905; J. Perrin, Traitd de chimie physique, 

 I, p. 142, 1903; and Lotka's Elements of Physical Biology, 1925, p. 26. 



t La Vie et la Mort, p. 81. § Philosophie Positive, Bk. rv. 



]| Ueber Entwicklung der Thiere: Beobachtungen und Reflexionen, i, p. 22, 1828. 



