6i6 



NA TURE 



[October 2; 



LETTERS TO THE EDITOR 



[ The Editor does not hold himself responsible for opinions ex- 

 pressed by his correspondents. Neither can he undertake 

 to return, or to correspond with the writers of, rejected 

 vianuscripfs intended for this or any other part of NATURE. 

 No notice is taken of anonymous cotnmunications.l 



Asymmetry and Vitalism, 

 In your issue of September 22, Prof. Pearson, referring to the 

 views expounded by Prof. Japp in his interesting address on 

 " Stereochemistry and Vitalism," shows that, if chance be the 

 only factor at work in the replacement of asymmetrical groups 

 in symmetrical molecules, the production in nature of an excess, 

 however, small, of compounds of one-sided asymmetry must un- 

 doubtedly have taken place. But, ignoring the mechanical inter- 

 pretation of the phenomenon (thus avoiding the stumbling-block 

 hinted at by Prof. Pearson), and taking, according to present 

 experience, for granted that, in the artificial introduction of 

 asymmetry into a symmetrical compound, equal amounts of 

 two inversely-active bodies are formed, so as to give rise to an 

 optically inactive mixture or compound (in a way recalling to 

 mind the separation of equal and corresponding amounts of 

 positive and negative electricity), other objections may, in my 

 opinion, be brought against Prof. Japp's views. 



The point at issue is this : out of inactive material, vegetal 

 and animal organisms are building up substances with asym- 

 metrical molecules, and optically-active, such as albumins and 

 carbohydrates. In which fact, joined with the chemists' then 

 ascertained inability to prepare artificial active compounds 

 from inactive substances, Pasteur saw an essential difference 

 between the forces that are acting in living nature and such as 

 are coming into play in our laboratories ; he called, accordingly, 

 the former asymmetrical, the latter symmetrical forces. This 

 alleged barrier fell to the ground after the successful preparation, 

 by Perkin and Duppa and by Jungfleisch, of racemic acid from 

 succinic acid, and the separation, Tjy means of a simple crystal- 

 lising process, of sodium ammonium racemate into dextro- and 

 Isevo-tartrate, differing by their inverse hemihedral faces, and 

 mechanically separable from one another. Being aware that the 

 spontaneous separation of racemic acid into its two active forms 

 afforded a strong argument against his theory, Pasteur uttered 

 the belief that, even in that phenomenon, some asymmetrical 

 outward agent, such as the organic germs contained in the 

 atmosphere, might be the separating cause ; but that hypothesis, 

 inadequately supported by Joubert and Bichat with the doubtful 

 evidence afforded by their experiments, cannot hold its ground 

 against the facts discovered by Scacchi and Wyrouboff, and 

 especially by Van 't Hoff and Deventer, respecting the so-called 

 "transition-point" of some double salts, a class of compounds 

 among which the racemates are but a particular case. 



On Prof. Japp's view the asymmetrical forces are brought into 

 play in another way and at another moment than on Pasteur's. 

 He contends that, while simple asymmetry (exemplified by dextro- 

 tartaric or laevotartaric acid) is caused by asymmetrical actions, 

 double asymmetry, as displayed by racemic acid, is caused by 

 symmetrical actions : no asymmetry comes into play in the latter 

 case, not even when the racemate is separating into its two 

 enantiomorphs, as for every right-handed crystal a corresponding 

 left-handed one is formed. But here is the point. When " the 

 two kinds of crystals are to be picked out, and placed each in a 

 vessel by itself," the intervention of an intelligent force, the 

 intelligent and living (whether mediate or immediate) act of 

 man is needed, as, both kinds having the same solubility, specific 

 gravity, melting point, &c. , behave in the same way towards all 

 the separating symmetrical and non-living agents we dispose 

 of in our laboratories. The conscious separation, carried out 

 by man, may be compared with the unconscious one caused 

 by bacteria and moulds, which agents are also able to destroy 

 one kind rather than the other : the common side of both actions 

 is that they are brought about by living organisms, formed of 

 asymmetrical material, and therefore able to act asymmetrically. 

 Now, granting that, according to Prof. Japp's interpretation 

 of facts, intervention of life cannot be dispensed with in the 

 above separation, I believe that, supposing no substance en- 

 dowed with molecular asymmetry to exist on our planet, it 

 would be, not merely conceivable, but actually possible to produce 

 as much simple asymmetry as might be desired, by means of an 

 amount of one racemic compound (such as some racemate) 

 liable to separation into active kinds, by the crystallising pro- 

 cess, without any interfering asymmetrical force. In point of 



NO. I 5 13, VOL. 58] 



fact, after the spontaneous separation (the suitable temperature 

 being granted) into the enantiomorphous crystals, we may always 

 imagine a force, neither intelligent nor living, and acting in a 

 symmetrical way, that would by chance single out one crystal : 

 from that single, asymmetrical crystal (whether right- or left- 

 handed), as was shown among other similar instances by Fischer 

 and Wallach, other compounds can, on introducing asym- 

 metrical groups, be prepared, displaying (without any previous 

 separation into enantiomorphs) simple asymmetry. For, while 

 a racemic compound always comes into existence when we 

 start the synthetic process with a symmetrical and therefore 

 ■ inactive substance, such is not the case when we are operating 

 on active, already asymmetrical compounds, as one active kind 

 rather than its enantiomorph (with respect to the newly-introduced 

 group) may be formed, the other one being partially or totally 

 excluded. The pre-existing asymmetry has a directing influence 

 upon the newly added atoms : asymmetry begets asymmetry, as 

 life begets life. This argument does not only fit the hypothesis 

 that a single crystal be selected : provided that the supposed 

 force act for so short a time as to allow but a small part of the 

 crystals to be removed, there is some chance for there being 

 an excess, however small, of either one or the other enantio- 

 morph to which the above remarks may as well apply. 



The following illustration may perhaps convey a clearer idea 

 of the fact stated. Supposing molecular asymmetry to have 

 come on to our planet from outward space (an origin ascribed 

 by some to life), let us imagine one primordial racemic com- 

 pound to have spontaneously separated into its two enantio- 

 morphs, and these to have been whirled round and scattered 

 about vacant space by some vortex, so as to allow one 

 simply asymmetrical particle to reach our globe. This may, 

 without the intervention of any peculiar force differing at all 

 from such as are acting in chemical .synthesis, have originated 

 all the now existent asymmetrical compounds. Some other 

 planet might nevertheless have been reached by a particle of 

 the other enantiomorph ; the ensuing molecular asymmetry 

 would accordingly have been the perfect reverse of ours : that 

 celestial body might be inhabited by living creatures akin to 

 ourselves, but built up of dextrogyrous albumins ; its vine- 

 grapes would yield /-glucose instead of i^ -glucose, &c. I do 

 not mean to contend that there is any probability of such events 

 having taken place, and am only pointing out that such an 

 hypothesis is in no way absurd or inconceivable. Nay, it might 

 even be enlarged. Although unlikely, a universe (in which our 

 planet might well be included) can be imagined, being formed 

 by pairs of celestial bodies endowed with equal and inverse 

 asymmetry, so as to be comparable with a set of enantiomor- 

 phous crystals, into which a mixture of racemous compounds 

 would separate. It matters little whether the enantiomorphs be 

 near one another, as in the case of a crystallising solution, or as 

 wide apart as the celestial bodies we are considering : there is 

 in both cases in a determinate point of space one kind of simple 

 asymmetry (the other one being excluded), a result attained 

 without any absolutely asymmetrical action, and especially life, 

 coming into play. 



That the way followed by living organisms in their pre- 

 paration of active substances, differs from the processes carried 

 on in laboratories, is quite another question : the capital point 

 is that, in one way as in the other, the final result is the same, 

 and that the formation of the first asymmetrical group is not 

 necessarily connected with that of the first living particle, as 

 Prof. Japp contends. In my opinion, the problem of spon- 

 taneous generation is not likely to be ever reduced to the far 

 simpler question of the origin of molecular asymmetry. 

 Turin, October. Giorgio Errera. 



I WILL endeavour to reply to the various criticisms which 

 have appeared in Nature on my address to the Chemical 

 Section of the British Association. 



Prof. Karl Pearson points out— what was, of course, obvious 

 — that if only a small number of asymmetric molecules — say 

 twenty — were to be formed under the influence of symmetric 

 forces, there might be a preponderance of either right- or left- 

 handed enantiomorphs, or even that all might be of one kind. 

 He then goes on to suggest that such asymmetric compounds 

 might have been spontaneously formed in the past, and might 

 " be endowed with a power of selecting their own asymmetry 

 from other racemoid compounds," and might thus act as 

 " breeders." 

 This is a view which, as I have found in private discussion, 



