September 2, 1920] 



NATURE 



with the Carnegie Trust, a million of the taxpayers' 

 money is now well on its way to provide more 

 sumptuous motor-cars rather than professors of 

 chemistry, and another two millions or so to foster 

 dye-making as it is understood in the City by directors 

 more innocent of the art than our early woad- 

 besmeared ancestors. To such ill-informed and costly 

 efforts the complete indifference with which science 

 was regarded in official circles before the war is surely 

 preferable. It may be dirticult to break with the habit 

 of a hundred years in patiently e.xpecting a miraculous 

 change of attitude on the part of the Government 

 towards the debt- and wealth-producing elements of 

 the community respectively. .V more practical and 

 practically attainable objective would, it seems to me, 

 be for the universities to ally themselves with Labour 

 to provide saner government. Incidentally, some long 

 overdue refonns of the universities might then be 

 effected, and the paralysing and deliberate strangle- 

 hold of the old vested interests upon science broken, 

 once for all. 



1 may merely be moi« outspoken than my col- 

 leagues, but I believe I am more scientific in diag- 

 nosing the trouble before seeking a remedy. The 

 failure of a century's efforts on the part of scientific 

 men is not due to ignorance, apathy, or any other 

 negative cause. But for the clever, tireless, and all- 

 embracing activities of all those to whom science 

 spells /irtjx, the existing absurdities would not survive 

 a vear, and against this combination Labour is the 

 only real force. The unpopularity of the proposed 

 remedy with all those who have proved themselves 

 such good friends of science in the past is, to my 

 mind, an unsolicited testimonial to its efficiency from 

 a quarter eminently in a position to judge. 



Frederick .Soddv. 



The Separation of the Isotopes of Chlorine. 

 In my letter to N.MfRE of June 17 I showed that 

 inappreciable s«'parability of the isotopes of chlorine 

 by a special class of chemical change w'ould Ix; difficult 

 to reconcile with Nernst's heat theorem, and in a 

 later issue of Nati;ke (July 15), at the request of 

 Prof. Soddy, the argument was more fully given. 

 Mr. Core (Nati'RE, July 29) has endeavoured to 

 remove the difficulty to which attention was directed 

 by me. With most of his deductions 1 agree, but I 

 am not satisfied that he has reconciled Nernst's theory 

 with the inappreciable /separability of the isotopes 

 bv the spoc'fietl chemical method. Mr. Core contends 

 that the solid compound CICI' which would actually 

 be formed in the chemical change represented by the 

 equation 



C1,-|-CI', = 2CICI' 



is a solid solution — ."since in the crystal the molecules 

 would be indifferently oriented as CICI' or CI'CI — 

 and Nernst's theorem cannot l>e applied to solutions. 

 Now Ncrnst states his theorem as follows : 

 " T have been led to the conclusion that not cnly 

 do .\ and I! become equal at the absolute zero of tem- 

 perature, but that their curves touch asymf>totirally 

 at this point. That is to say, 



lim^ = l)m''!I(forT-o). 

 rfT i/T ' 



It is to be remembered that this equation is onlv 

 slrictlv anplicahle to pure solid or liquid substances " 

 fH. T. Tizard's translation of Nernst's "Theoretical 

 Chemistry," ini6 edition, p. 746). 



.Again. Nernst {\oc. cit., p. 748) identifies liquid with 

 amorphous substances 



Further, Planck limits the annlication of his more 

 general enunciation of Nernst's theorem to chemicallv 



NO. 2653, VOL. 106] 



homogeneous substances, which he defines as sub- 

 stances made up of nothing but molecules of the jame 

 kind (Max Planck, " Thermodynamik," § 67). 



Neither of these definitions appears to me to exclude 

 the crystalline modifications of CICI', which are stable 

 at finite temperatures. But even if it be conceded 

 that the intention w'as to exclude such solid com- 

 pounds, the difficulty I find in reconciling Nernst's 

 heat theorem with the inappreciable separability of 

 the isotopes by the specified chemical method has not 

 been removed, for the solid substances taken in per- 

 forming the thermodynamic cycles can ' (without 

 modifying the reasoning) be the liquid (amorphous) 

 forms. D. L. Chapman. 



Jesus College, Oxford. 



.The Scratch-Reflex in the Cat. 



I HAD lately the opportunity of examining in a 

 young cat eight weeks old the conditions of the 

 scratch-reflex, and the results would seem to be 

 worth noting. The animal had been through an 

 unusually heavy day of play on a hot day, and in the 

 evening was lying asleep on the lap of one of her 

 friends in a profound sleep. I thought this a good 

 occasion for finding out what reactions she would 

 show to gentle mechanical stimuli. A very light 

 touch with a wooden match on the conchal surface 

 of the pinna, or one extending to the meatus, pro- 

 duced immediate response as follows : — First, the 

 facial muscles on the same side twitched irregularly ; 

 this ceased, and then the fore foot was moved irregu- 

 larly towards, but not so far as, the ear ; when this 

 had ceased there occurred at once a rhythmical move- 

 ment of the hind limb, with a rate closely similar to 

 that of the scratch-reflex of the dog, the hind foot, 

 as in the fore foot, being brought towards, but not 

 up to, the ear. 



This unusual sleep lasted for a quarter of an hour, 

 during which repeated light mechanical stimuli of 

 various kinds failed to wake the animal, and the 

 above series of reactions was frequently evoked, but 

 none of the later attempts produced results so strongly 

 marked as the first. I was unfortunate then in not 

 having read more than an abstract of the paper in 

 the Journal of Physiology of December, 1917, by 

 Prof. Sherrington on "The Pinna Reflexes in the 

 Cat." He has now very kindly sent me a copv of 

 the paper, and I see how much better I might iiave 

 marked out the receptive field of this reflex if 1 had 

 know^n the accurate observations he has made on it. 



I examined in this animal then and since the 

 various regions of the back and flanks, and have 

 found there no receptive field like that of the dog, 

 which s<'ems to be in accordance with the exp«>rienc« 

 of others. Since the first occasion 1 have found the 

 foregoing reactions pres<-nt many times, but the sleep 

 has always been lighter and the results less orderly 

 and striking. Walter Kinn. 



Chalet le Mourezin, Ch.'iteau d'Oex, 

 ' Switzerland, .\ugust 13. 



Portraits Wanted. 



I SHOULD greatly appreciate any information readers 

 of Nati^RK may be able to give me which would lead 

 to the discovery of portraits of any of the following; 

 early myriapodologists ;— .Shaw (who publislvd a 

 paper in 1789, Trans. Linn. .Soc.. vol. ii.. p. 7), 

 W. E. I-each, Oeortje Newport, John Fdward Gray, 

 and John Curtis. The Inst four all published papers 

 during tlie first half of th<' nineteenth cenlurv. 



S. Graham Bradr-Birks. 



16 Bank .Street, Darwen, I^ncs, .\ugust 19. 



