EVOLUTION AND THERMODYNAMICS 



organism is. Among the higher types decrease in number of repro- 

 ductive products and corresponding increase of parental care illustrate 

 this, and vast chapters of comparative physiology and biochemistry 

 are devoted to the origin and development in evolution of body- 

 temperature regulation, desiccation control, adjustment of the compo- 

 sition of the blood and the like. "The constancy of the internal 

 medium," said Claude Bernard, in an aphorism popularised by 

 Barcroft,^ "is the condition of all free life." Nor is there in purposive- 

 ness anything that lies outside the scientific frame of reference. The 

 Aristotelian theory of causation is irrelevant. Biological purposiveness 

 and adaptation are concepts inseparable from biological facts, and as 

 Donnan^ has shown, there exist branches of mathematics, such as 

 integro-differential equations, which may be able to cope with systems 

 whose behaviour differs according to their past history. Consciousness 

 is the highest phase of this behaviour and when the organisational 

 level is reached at which psychological phenomena first appear, 

 sociological phenomena appear too. One may say that biological 

 organisation is as much an organisation of processes as of structures. 

 The point at issue is, then, whether the concepts of organisation 

 as used by physicists and by biologists have anything in common.^ 



The Two Concepts of Organisation. 



It is curious that this difficulty has not been more widely felt. 

 Some thinkers have, indeed, been acutely troubled by it, for instance 

 Rusk,* who spoke of a "conflict of currents," the physical world 

 losing organisation and the biological world gaining it; and Ralph 

 Lillie,^ who opposed in an "apparent paradox" the "diversifying 

 tendency" of evolution to the "dissipative tendency" making for 



^ "La Fixite du Milieu Interieur est la Condition de la Vie litre," by J. Barcroft, Biol. 

 Rev., 1932,7, 24; and later as part of his book Features in the Architecture of Physiological 

 Function (Cambridge, 1934). 



^ F. G. Donnan in Acta Biotheoretica, 1936, 2, i. 

 ■ ^ We consider mainly in this survey the rise in level of organisation during phylo- 

 genesis (evolution). But embryologists also see a rise in level of organisation during 

 ontogenesis (the growth and differentiation of the individual). So far as we know, 

 nothing that happens during embryonic development infringes the second law, and apart 

 from the energy turnover in metabolic upkeep during development, there is little or 

 no energy associated with the highly complex finished structure. For further information 

 on tliis difficult subject see the section on energetics in Chemical Embryology (by 

 J. Needham', Cambridge, 193 1) and the review of O. Meyerhof (Handbuch d. Physik, 

 T026, 11, 243). 



* R. D. Rusk, Atoms, Man and Stars (New York, 1937), p. 273. 



^ R. S. Lillie, Amer. Nat,, 1934, 68, 318; Philos. of Sci., 1934, 1, 297. 



