4 o8 SCIENCE PROGRESS 



variables and the parameters appearing in them. 1 Until this 

 is done the mere statement that such functions exist is of 

 little value, except, perhaps, as pointing a certain direction 

 for inquiry. Needless to say, the statement that such func- 

 tions, relative to a system in the course of organic evolution, 

 exist, lacks entirely the rigorous basis on which rest the corre- 

 sponding propositions regarding the evolution of physical 

 systems under certain clearly defined conditions. 



It seems, therefore, worth noting that a process of organic 

 evolution, when viewed or comprehended from a certain 

 standpoint, falls naturally within a definite category or class 

 comprising also that group of physical phenomena termed 

 " change of state." 2 The fit is so complete that the same 

 general method of analytical treatment can be applied, without 

 distinction, to the entire category ; and certain general con- 

 clusions relating equally to " change of state," as ordinarily 

 understood, and to certain phenomena in an evolving organic 

 system, follow in natural course. 



This viewpoint is gained by regarding the evolution of the 

 system under consideration as the redistribution of matter 

 among the components of the evolving system. 



In the case of an ordinary physico-chemical system, for 

 example, the system may consist of the three components 3 

 H 2 , 2 , H 2 0, and in the course of the evolution of the system, 

 matter redistributes itself among these components in accor- 

 dance with a certain system of differential equations : 



= F x (X lt X„ X 3 ; p, T) 



dt 

 d § = FJ& U X* X 3 ; p, T) 



d f = F 3 (X ly X*, X 3 ; p, T) 



(1) 



1 Similar remarks apply to various attempts to apply to biological systems the 

 Principle of Le Chatelier. Inasmuch as this principle itself derives its validity 

 from the second law of thermodynamics, its application can be regarded as 

 established only for those systems and for those variables and parameters which 

 we are competent to-day to treat by thermodynamical methods. The principle is 

 quite meaningless unless the particular variables to which it is applied are clearly 

 stated. Even then, and in the case of simple physical systems, the application of 

 the principle is very liable to errors, of which the literature gives ample illustra- 

 tion. (See Ehrenfest, Zeitschr. Jur Phys. Chem., 191 1, vol. lxxvii, p. 735 ; Wol- 

 chonsky, Jour. Russian Phys. Chem. Soc., 1912, vol. xliv, pp. 305, 310; Chwolson, 

 Lehrbuch der Phys., 1909, vol. iii, p. 547 ; Bancroft, Jour. Amer. Chem. Soc, 

 191 1, p. 92; Fournier d'Albe, Contemporary Chemistry, 191 1, p. 38; Lowy, 

 Kosmos, 191 1, p. 331 ; Le Dantec, La Stabilite de la Vie, 1910, p. 25 ; Spencer, 

 First Principles, chap, xxii, section 173, Burt's Edition, p. 433). 



2 This term is here used in a general sense, to include also change of state by 

 chemical reaction. 3 Not necessarily independent. 



