September 8, 1898 J 



NATURE 



459 



view, and suggested that the formation of chemical compounds 

 in the magnetic field, or under the influence of circularly 

 polarised light, would furnish a means of solving the problem ; 

 and Van 't Hoff also thinks the latter method feasible. As regards 

 magnetism, Pasteur's suggestion was undoubtedly based on a 

 misconception ; the magnetic field has not an asymmetric struc- 

 ture ; it is merely polar, since the rotation which it produces in 

 the plane of polarisation of a ray of light changes sign with the 

 direction of the field. As regards circularly polarised light, I 

 must confess to having doubts as to whether it can be regarded 

 as an asymmetric phenomenon : the motion of the ether about 

 the axis of the ray is circular, not spiral ; and it is only by con- 

 sidering the difference of phase from point to point along the 

 ray that the idea of a spiral can be evolved from it. In fact, 

 are there such things as forces asymmetric in themselves ? Is 

 the geometrical conception of asymmetry applicable to dynamical 

 phenomena at all, except in so far as these deal with asymmetric 

 material structures, such as quartz crystals, or organic molecules 

 containing asymmetric carbon atoms ? But this is a question 

 which I would submit to the judgment of mathematical 

 physicists. 



One thing is certain — namely, that all attempts to form optic- 

 ally active compounds under the influence of magnetism or cir- 

 cularly polarised light have hitherto signally failed. These forces 

 do not distinguish between the two equally exposed points of 

 attack which present themselves in the final stage of the trans- 

 formation of a symmetric into an asymmetric carbon atom. 



But even if such an asymmetric force could be discovered — a 

 force which would enable us to synthesise a single enantiomorph 

 — the process would not be free from the intervention of life. 

 Such a force would necessarily be capable of acting in two 

 opposite asymmetric senses ; left to itself it would act impar- 

 tially in either sense, producing, in the end, both enantiomorphs 

 in equal amount. Only the free choice of the living operator 

 could direct it consistently into one of its two possible channels. 

 I will briefly recapitulate the conclusions at which we have 

 arrived. Non-living symmetrical matter — the matter of which 

 the inorganic world is composed — interacting under the influence 

 of symmetric forces to form asymmetric compounds, always 

 yields either pairs of enantiomorphous molecules (racemoid 

 form), or pairs of enantiomorphous groups united within the 

 molecule (meso-form), the result being, in either case, mutual 

 compensation and consequent optical inactivity. The same will 

 hold good of symmetric matter interacting under the influence 

 of asymmetric forces (supposing that such forces exist) provided 

 that the latter are left to produce their effect under conditions of 

 pure chance. 



If these conclusions are correct, as I believe they are, then the 

 absolute origin of the compounds of one-sided asymmetry to 

 be found in the living world is a mystery as profound as the 

 absolute origin of life itself. The two phenomena are inti- 

 mately connected for, as we have seen, these symmetric com- 

 pounds make their appearance with life, and are inseparable 

 arom it. 



r How, for example, could Isevo-rotatory protein (or whatever 

 the first asymmetric compound may have been) be spontaneously 

 generated in a world of symmetric matter and of forces which 

 are either symmetric or, if asymmetric, are asymmetric in two 

 opposite senses ? What mechanism could account for such 

 selective production ? Or if, on the other hand, we suppose 

 that dextro- and Irevo-protein were simultaneously formed, 

 what conditions of environment existing in such a world could 

 account for the survival of the one form and the disappearance 

 of the other ? Natural selection leaves us in the lurch here ; 

 for selective consumption is, under these conditions, as incon- 

 ceivable as selective production. 



No fortuitous concourse of atoms, even with all eternity for 

 them to clash and combine in, could compass this feat of the 

 formation of the first optically active organic compound. Co- 

 incidence is excluded, and every purely mechanical explanation 

 of the phenomenon must necessarily fail. 



I see no escape from the conclusion that, at the moment when 

 life first arose, a directive force came into play — a force of pre- 

 cisely the same character as that which enables the intelligent 

 operator, by the exercise of his Will, to select one crystallised 

 enantiomorph and reject its asymmetric opposite. 



I would emphasise the fact that the operation of a directive 

 force of this nature does not involve a violation of the law of 

 the conservation of energy. Enantiomorphs have the same 

 heat of formation ; the heat of transformation of one form into 



NO. 1506, VOL. 58] 



the other is nil. Whether, therefore, one enantiomorph alone 

 is formed, or its optical opposite alone, or a mixture of both, 

 the energy required per unit weight of substance is the same. 

 There will be no dishonoured drafts on the unalterable fund of 

 energy. 



The interest of the phenomena of molecular asymmetry from 

 the point of view of the biologist lies in the fact that they reduce 

 to its simplest issues the question of the possibility or impossi- 

 bility of living matter originating from dead matter by a purely 

 mechanical process. They reduce it to a question of solid 

 geometry and elementary dynamics ; and therefore if the at- 

 tempted mechanical explanation leads to a redtictio ad absurdum, 

 this ought to be of a correspondingly simple and convincing 

 character. Let us see how far this is the case. 



Life is a phenomenon of bewildering complexity. But in 

 discussing the problem of the origin of life, this complexity cuts 

 two ways. Whilst, on the one hand, it is appealed to by one 

 set of disputants as an argument against the mechanical theory, 

 on the other it affords shelter for the most unproved statements 

 of their opponents. I will take a concrete instance from the 

 writings of an upholder of the mechanical theory of the origin 

 of life, the late Prof. W. K. Cliff"ord. He says : 



"Those persons who believe that living matter, such as pro- 

 tein, arises out of non-living matter in the sea, suppose that it is 

 formed like all other chemical compounds. That is to say, it 

 originates in a coincidence, and is preserved by natural selection. 

 . . . The coincidence involved in the formation of a molecule so 

 complex as to be called living, must be, so far as we can make 

 out, a very elaborate coincidence. But how often does it happen 

 in a cubic mile of sea- water ? Perhaps once a week ; perhaps 

 once in many centuries ; perhaps, also, many million times a 

 day. From this living molecule to a speck of protoplasm visible 

 in the microscope is a very far cry ; involving, it may be, a 

 thousand years or so of evolution." 



It was easy for Clifford to write thus concerning life itself, for 

 it was difiicuit for any one to contradict him. But had he been 

 asked whether any mechanical (symmetric) coincidence would 

 ■ suffice to convert an infinitely great number of molecules of the 

 type shown in Fig. 3 into that shown in (say) Fig. i, to the ex- 

 clusion of that shown in Fig. 2 ; or whether, given a mixture, 

 in equal proportions, of molecules of the types shown in Figs. I 

 and 2, any mechanical (symmetric) conditions of environment 

 would bring about the destruction of one kind and the survival 

 of the other, I think his exact mathematical and dynamical 

 knowledge would have prevented him from giving an affirmative 

 answer. But short of this affirmative answer, his other state- 

 ments, it seems to me, fall to the ground. 



I am convinced that the tenacity with which Pasteur fought 

 against the doctrine of spontaneous generation was not uncon- 

 nected with his belief that chemical compounds of one-sided 

 asymmetry could not arise save under the influence of life. 



Should any one object that the doctrine of the asymmetric 

 carbon atom is a somewhat hypothetical foundation on which to 

 build such a superstructure of argument as the foregoing, I 

 would point out that the argument is in reality independent of 

 this doctrine. All that I have said regarding the molecular 

 asymmetry of naturally occurring optically active organic com- 

 pounds, and all the geometrical considerations based thereon, 

 hold good equally of the hemihedral crystalline forms of these 

 compounds, about which there is no hypothesis at all. The 

 production of a compound crystallising in one hemihedral form 

 to the exclusion of the opposite hemihedral form, as in the case 

 of the tartaric acid of the grape, is a phenomenon inexplicable 

 on the assumption that merely mechanical, symmetric forces 

 are at work. Nor is this conclusion invalidated even if we ulti- 

 mately have to admit that the connection between molecular 

 and crystalline asymmetry is not an invariable one — a point 

 about which there is some dispute. 



At the close of the lectures from which I have so frequently 

 quoted, Pasteur, with full confidence in the importance of his 

 work, but without any trace of personal vanity, says : — 



*' It is the theory of molecular asymmetry that we have just 

 established — one of the most exalted chapters of science. It 

 was completely unforeseen, and opens to physiology new 

 horizons, distant but sure." 



I must leave physiologists to judge how far they have availed 

 themselves of the new outlook which Pasteur opened up to 

 them. But if I have in any way cleared the view towards one of 

 these horizons, I shall feel that I have not occupied this chair in 



