54 SECTIONAL ADDRESSES 



It would be out of place to attempt to pursue this in detail. I wish 

 merely to emphasise the conclusion that if the reactions of living matter 

 are as stereo-specific as the optical activity of the products indicates that 

 they are, and if, further, a diminution in the concentration of a reactant 

 in a biochemical process produces a comparable diminution in the reaction 

 velocity, as the study of enzyme actions indicates may be the case as 

 long as certain limits of concentration are not exceeded, then the synthesis 

 of the components of new tissue will proceed more rapidly in living 

 matter constituted, as we now find it, with all its dissymmetric components 

 present in correlated optically active forms, than it would in living matter 

 otherwise identical but optically inactive. 



Let us now consider the gro^vth of a tissue which is not completely 

 optically inactive, that is, a tissue in which the d- and /-systems are not 

 present in equal quantities. 



Let us suppose, for example, that there is twice as much of the <^-system 

 as of the /-system. 



It is clear, if the arguments which I have put forward are valid, that 

 in the process of groAVth of a tissue thus constituted, the ^-system will 

 increase at a relatively greater rate than the /-system. 



The complex dissymmetric components of the new tissue will be built 

 up from the simple symmetrical food-materials by chains of synthetic 

 reactions and the rates of formation of the end-products will be controlled 

 by the velocity of the slowest link in the chains. If we consider a case 

 in which, as must frequently happen, this slowest link is an interaction 

 involving two dissymmetric molecules, and if we suppose that the applica- 

 tion of the law of mass action is so little obscured by adsorption phenomena 

 that we may with sufficient approximation assume that, as in a simple 

 bimolecular reaction, the reaction velocity is proportional to the second 

 power of the concentration, then the rate of formation of the ^-component 

 will be four times that of its enantiomorph. If this applied to every 

 dissymmetric constituent of the new growth, then, whereas there was 

 twice as much of the d- as of the /-system in the old tissue, there would 

 be four times as much of the d- as of the /-system in the new growth. 



It will be clear that, even though the reactions of living matter may be 

 less completely stereo-specific than I have, for simplicity, assumed, and 

 though the velocities of the bi- and poly-molecular reactions in question 

 may increase more slowly with the concentration than according to the 

 second power, yet as long as they increase more rapidly than according 

 to the first power of the concentration any excess of one system over the 

 other in the old tissue will become greater in the new growth. 



In a subject as complicated as this, and where precise knowledge is so 

 lacking, it is not possible to give an exact proof, but I hope I may have 

 succeeded in indicating that there is an a priori probability that an 

 optically inactive growing tissue would be, as regards its optical inactivity, 

 in a state of unstable equilibrium. If there were the slightest departure 

 in either direction from exact equality of the d- and /-components of the 

 tissue, this would increase with growth continually, according to a com- 

 pound interest law until, eventually, the system originally in slight defect 

 was completely swamped by its enantiomorph. 



