SESSION V. DISCUSSION 487 



in the stationary state. It seems to me, however, that the direct comparison of the rate 

 of development of entropy and the intensity of metabolic processes made in Prof. 

 Prigogine's work is scarcely proper, especially when this principle is being put forward 

 as the driving force of the process of evolution (e.g. in the works of Prigogine and Viames). 

 This concept does not agree with the factual evidence, for Netter has shown that the 

 uptake of oxygen per unit mass by Paramoeciiim is similar to that of vertebrates; it is 

 inacceptable even on theoretical grounds since the entropie characteristic is regular, but 

 is, in principle, insufficient for the analysis of biochemical processes. Changes in the 

 metaboUsm of Uving organisms are directed to improving their adaptation to the con- 

 ditions of their existence and are not in any way determined by the level of production of 

 entropy. It is probable that any level of production of entropy could be estabhshed by 

 evolution, though it would, of course, be at the expense of the uptake of a sufficient 

 quantity of energy from the medium. 



The next question concerns the limits of applicability of linear relationships between 

 the rates of reactions and changes in the expression Au = LôAp, applied to the thermo- 

 dynamics of irreversible processes. According to the evidence of Eyring and his col- 

 leagues these linear relationships (with an accuracy of about io%), are limited to 

 changes AF --^ 02 kcal/mole. These are, certainly, very narrow limits, in biochemical 

 processes, even when they occur by many stages AF > 1-2 kcal/mole. The question then 

 arises as to whether it is possible to extend the theory by making use of non-linear terms, 

 and I should like to be clear about Prof. Prigogine's ideas on this possibility. In the third 

 place I should like to consider the kinetic aspect of the direction of reactions in open 

 systems. The basic principle here is the idea, formulated by Hinshelwood, that, within 

 the network of connected chemical reactions in an open system, the direction of the 

 chemical reactions is determined by the principle of maximal rate of the reactions. This 

 formulation is not concerned with the molecular mechanism of the reactions and it may, 

 therefore, be taken in conjunction with Prof. Prigogine's principle determining the 

 thermodynamic criteria for the direction of processes in the system and their approxi- 

 mation to the stationary state. In essence, these principles also determine the evolution 

 of chemical systems in the prebiological stage of development which has also been dis- 

 cussed by Prof. Calvin, though the factors which he adduced (the presence of sources of 

 energy, autocatalysis, etc.) are partial phenomena of the Hinshelwood-Prigogine principle. 

 It may also be pointed out that there is a close connection between the 'dynamic state', 

 considered by Prof. Broda, and the theory of open systems. I should like to conclude 

 with the hope that there will be a successful development of the theory of open systems 

 which is of great biological importance, especially for the problem of the origin of life. 



K. S. Trincher (U.S.S.R.): 



The Principle of the Acceleration of the Ittcrease of Entropy of a Closed 

 System as the Physical Basis of Vital Processes 



Let us consider a closed system undergoing energy exchange with the external medium 

 and having, in the stationary state, a constant potential (chemical) energy in the form of 

 macroergic substances. The closed system consists of a collection of open or living systems 

 and the medium surrounding them. In an open system there occur irreversible processes 

 consisting in the transformation of the chemical energy of the macroergic substances. In 

 the course of the irreversible changes 'uncompensated heat' [i] is formed (eq. i) and 

 entropy arises : 



rd^irrev. = d^. (l) 



Let us suppose that the chemical reactions are the only reason for the irreversibility, 

 the rate of increase of entropy will then be : 



dt /irrev. df 



