56 SECTIONAL ADDRESSES 



I am indebted to Mr. L. A. Pars for calculating the very simple relation 

 which exists between the average degree of dissymmetry k and the number 

 of molecules n, when n is large. It is 



k=^ o-6743/\/« 

 Thus the average degree of dissymmetry sinks to 0-067 P^r '^^^^^ ^^^ 

 one million and to 0-021 per cent, for ten million molecules. In other 

 words, when ten million dissymmetric molecules are produced under 

 conditions which favour neither enantiomorph, there is an even chance 

 that the product will contain an excess of more than 0-021 per cent, of 

 one enantiomorph or the other. It is practically impossible for the 

 product to be absolutely optically inactive. It is more probable than 

 not that it will possess a very small but nevertheless a finite optical activity, 

 exceeding o -021 per cent, of that of the optically pure substance. 



Of course, ten million molecules represents a quantity of matter which 

 is exceedingly minute in comparison with the quantities that chemists are 

 accustomed to handle. To gain a concrete notion of the magnitudes 

 involved, we may imagine a catalytically active compound of a molecular 

 weight of 35,000, and, with regard to the well-established biological 

 potency of very small quantities of many substances, we may suppose 

 that it exerts a marked influence on the metabolism of living matter 

 when present at a concentration of o- 1 per cent. Ten million molecules 

 of this substance would then be contained in- a sphere of protoplasm of 

 three hundredths of a millimetre, or 30 \j. in diameter. 



This is at least a thousand times as large (in bulk) as the smallest 

 forms of vegetable life. A number of green algae and some of the 

 smallest blue-green algae are only 3 [j. in their larger diameter. 



In microscopic forms of life it appears, therefore, by no means impos- 

 sible that the number of molecules of one vitally dominant dissymmetric 

 catalyst contained in an organism might be sufficiently low to ensure 

 the probability of the presence of a small but finite relative excess of one 

 of the enantiomorphous forms, when that quantity of the compound was 

 produced under symmetrical conditions. 



If we could assume, therefore, that the first portion of living matter 

 which arose on this planet was of microscopic dimensions, we might 

 account on the basis of the laws of probability for the existence of a minute 

 initial bias towards one optical system or the other ; and this would 

 then, if the principles which I have endeavoured to explain are justified, 

 eventually lead to the complete optical activity of the molecularly dis- 

 symmetric components of all living matter. The development of the 

 organic kingdom from a single germ would provide a simple explanation 

 of the configurational relationship which appears to exist between the 

 optically active components of the most diverse forms of life , as is illustrated 

 by the occurrence in nature of glucose in its dextro-rotatory form only. 

 The mystery of living matter seems to lie in its power of growth. Given 

 this, the optical activity of its components appears to follow as a necessary 

 consequence of the law of mass action and the stereo-specificity of inter- 

 actions between dissymmetric compounds. 



