30 



NA TURE 



[November io, i! 



(Naturk, vol. Iviii. p. 592, col. 2) so as to include these special 

 cases. 



Similar considerations would apply to the action of polarised 

 !is;ht on a mixture of enantiomorphs. The most that could 

 occur would be the production of an equal rotation of enantio- 

 morphous molecules in opposite senses, corresponding with their 

 opposite asymmetry. That would not cause separation. 



Again, take Mr. Spencer's first "abstract proposition" (loc. 

 (it.), which runs : " I.iUe units subject to a uniform force capable 

 of producing motion in them, will be moved to like degrees in 

 the same direction." How does he reconcile this statement with 

 the fact that enantiomorphs have the same heat of formation : 

 i.e. that the same atoms are moved by the same amounts 

 of energy, not in the same direction, but in directions of 

 opposite asymmetry, so as to form two asymmetrically distinct 

 compounds ? 



I probably do Mr. Spencer no iniustice if I assume that in 

 1S62, when he formulated these " abstract propositions," he was 

 not acquainted with the theory of molecular asymmetry, which 

 at that time was not generally current, even among professed 

 chemists. And if I might do so without offence, I would suggest 

 that he should read the portion of Van 't Hofi's " Arrangement 

 of Atoms in Space " (second edition) dealing with the question 

 of molecular asymmetry, especially the section which describes 

 the character of the isomerism due to the asymmetric carbon 

 atom. He may then be able to recast his "abstract pro- 

 positions " so as to include, at least more explicitly, the form- 

 ation and behaviour of enantiomorphous molecules under 

 symmetric influences F. R. Jatp. 



The Univeisity, Aberdeen, November 2. 



I AM not sure that much is to be gained by continuing this 

 discussion further, but perhaps I may be permitted to add 

 something to my first criticism of Prof. Japp's standpoint in 

 view of his communication in last week's Nature. 



The statement of Prof. Japp's, which I specially criticised, 

 was the following (where I italicise the words to which I wish 

 to draw particular attention) : — But the ihance synthesis of the 

 simplest optically active compound from inorganic materials is 

 absolutely ituonceivable. 



To this I replied and still reply, it is not absolutely incon- 

 ceivable. An optically active compound means merely a 

 preponderance of one kind of enaniiumorph, and chance will 

 always produce this, given enough trials and length of time to 

 make them. Prof. Japp twits me with the ineffectiveness of 

 twenty molecules, but I spoke not of twenty molecules, but of 

 twenty coins, in order to bring home to Prof. Japp what a 

 deviation from the average in the theory of chance really means. 

 The probability of a deviation of 5000 in 1,000,000 molecules 

 is easily calculated, and such a deviation is quite " conceivable," 

 even if it be very infrequent. A deviation of 5000 in 

 1,000,000 molecules would give an optically active solution, 

 whether sufficiently intense to be observed by the means at our 

 disposal is another question. The statement that on the theory 

 of chance, an optically active compound is absolutely inconceiv- 

 able is, I take it, absurd. It may be very improbable, but this 

 is not the term used by Prof. Japp. 



Prof. Japp writes in his letter : " Prof. Pearson's twenty non- 

 living asymmetrical molecules formed by the chance play of 

 mechanical forces, would, so far as experiment informs us — 

 although I freely admit that mere negative results are not 

 conclusive — have no more influence on the asymmetry of other 

 molecules formed in their neighbourhood than one toss of a coin 

 has upon another toss." I reply that I think experiment shows 

 they have. It is possible in Jungfieisch's process to get crystals 

 which are purely right- or left-handed up to the size, say, of 

 half an inch, sufticiently large for picking out. Now I take it 

 that it is chance which produces a slight majority of one type of 

 enantiomorphs at one or other point, and what I have termed 

 " breeding," which encourages the collection of that type at the 

 given centre until we get crystals purely right- or left-handed up 

 to a size of half an inch. That a number of molecules of one 

 kind, such as are required for these crystals, should be 

 frequently formed, is totally opjiosed to the theory of chance, 

 but I take it that a slight chance preponderance sets the 

 " breeding" going. 



Take a dish of such crystals and throw them out at random, 

 and they scatter in all directions ; one such crystal coming into 

 a few drops of fluid forms an optically active medium consisting 

 of enantiomorphs of one kind only. Thus even a total dis- 



NO. 15 15, VOL. 59] 



appearance of one kind of enantiomorphs is not impossible, or 

 "absolutely inconceivable" on the theory of chance. Prof. 

 Japp speaks of the " vague and elastic " way in which I speak 

 of the " breeding ' process — I notice that Prof. Errera also 

 uses the phrase "asymmetry begets asymmetry as life begets 

 life." Let us confine the term then, for the present, simply to 

 the process (of which so far the mechanism is unintelligible) by 

 which chance having given a slight local preponderance of one 

 type of enantiomorph, a group of the same type, visible and 

 touchable, is formed there. It is jierfectly conceivable that 

 this is only a visible representation of the process by which 

 living asymmetry selects its like, even in a non-crystalline 

 compound. It is only the mechanism which is vague, not the 

 fact. 



Prof. Japp really complains in his address that an " eminent 

 physicist " .should s.iy that an explanation of rotatory polaris- 

 ation is still wanting. It is still wanting, because no kinetic 

 theory, which is what a physicist requires, can l>e provided 

 by what is after all only a geometrical schema of the chemist. 

 Prof. Japp now writes th.it every chemist recognises that 

 it is only a geometrical hypothesis, and he did not think so 

 obvious a qualification needed statement to an audience of 

 chemists. Then why, I ask, should Prof. Japp go out of his | 

 way to say that the theory was unknown outside the circle of I 

 organic chemists, and cite the "eminent physicist" as an j 

 example of .such ignorance? I 



The fact is, that the moment we look at Prof. Japp's tetra- | 

 hedron atoms. Figs, i and 2 of his paper, as </)•»/<»«/ /Va/ systems, 

 the right-handed and left-handed molecules do not res|)ond in 

 the same manner to symmetrical forces. The atoms not being 

 identical, the centroid will not necessarily be the centroid of 

 the tetrahedron ; say. it is somewhat nearer to Z' than H. Now 

 whirl a thin cylindrical sheet of optically inactive mixture round 

 the axis of the sheet, left- or right-handed rotation is indifferent ; 

 the left-handed tetrahedra will not be in stable equilibrium 

 relatively to the centroid of the molecule in the same position 

 as the right-handed. Con.sequently the former will all set, say, 

 their X' angle inwards, and the latter outwards : or at least 

 some similar like dift'erence of positions will dift'erentiate like 

 from unlike enantiomorphs. Now let a strip of the cylindrical 

 surface be placed horizontally and allowed to fall, sav. through 

 a viscous fluid, the resistance to a tetrahedron going X' foremost, 

 may well be greater or less than one going HZ'V foremost, 

 and if so the left-handed molecules will be separated ultimately 

 from the right. .-Ml this is purely hypothetical, but I introduce 

 it because Prof. Japp asserts that it is " impossible ' for any 

 mechanical (symmetrical) forces to constantly select one of two 

 opposite forms. I reply that the impossible is conceivable, if 

 he will treat his molecules not as geometrical schemas, but a!> 

 dynamical systems. 



One last word. Prof. Japp refers in his address to a "vital 

 force " which does not disobey the law of energy, but is purely 

 directive of motion. I have seen such an idea several times 

 mooted. The question is not, however, if something called 

 vital force obeys the law of the conservation of energy-, for the 

 principle of energy never fully defined any motion, something 

 else is also directly or tacitly assumed. In itself it only le.ads 

 to one equation, not sufficient to describe any motion. "The 

 problem is whether "vital force" obeys all the laws of motion 

 — for example the conservation of momentum, angular and 

 linear, which it could hardly do if it changed the direction of 

 motion. I am <|uite unable to realise why some chemists and 

 physicists seem to think a disregard for the conservation of 

 momentum less miraculous than a disregard for the ci'nservation 

 of energy. I do not see why the le-ss important principle should 

 be made more of a fetish than the wider reaching principle. It 

 "vital force" does obey all the laws of motion, then it can 

 only be a rathet bad name for some piece of mechanism, to 

 which the most ardent supporter of a mechanical theory of the 

 univer.se (such as Biichner or .Moleschott, not I) could not 

 possibly object. Kari. Pearson. 



University College. 



Whilst Prof. Japp is to some extent justified in saying that 

 all his critics "seem to be moving in that unreal world where 

 a fount of type, if jumbled together sufficiently often, ends by 

 setting up the text of I/anilet,'' still it must be borne in mind 

 that he himself provoked a discussion in such an imagiiiary 

 region by raising the question as to the possibility of produciiig, 

 without the interference of a living agency, an optically active 



