12| 



NATURE 



[October 17. [918 



graphical sialics. They arc well devised and \er\ 

 put to the candidates. The wording is 

 often such .is to acl persuasively on the examinees. 

 That the questions arc also up to date is indicated 

 by the presence of some on aeroplanes and kites. 



Answers arc given b\ the editOl in ihc case of 



questions oJ a mathematical or arithmetical nature. 

 There is a misprint on |>. 1 1 "I the "Mathematical 

 Papers," line <> from the bottom. S. B. 



A Short Hand-book 0) Oil Analysis. By Dr. 

 A. II. Gill. Revised eighth edition, Pp. 209. 

 (Philadelphia and London: J. B. LippincoO 

 Co., [918.) Price tos. 6d. net. 



This is a handy little book for a student of oil 

 chemistry to commence His technical practice with. 

 It is intended as an introduction to larger works 

 such as thai "1 Lewkowitsch, and deals with the 

 chief animal and vegetable oils, petroleum pro- 

 ducts, and the various greases used as lubricants. 

 It gi\rs the essential information briefly but 

 clearly, and includes a good number of references 

 iriginal sources of information. The volume 

 is written from the American point of view, and 

 some of the apparatus mentioned is more familiar 

 in American laboratories than in this country. 

 Some of the books quoted, also, are not readilv 

 accessible here. The British reader, however, will 

 have no difficulty with the greater part of the' 

 work, and he will find it a very useful guide. 

 The first paragraph on p. 175 wants revision: 

 it appears to have suffered in the press. 



LETTERS TO THE EDITOR. 

 [The Editor does not hold himself responsible for 

 opinions expressed by his correspondents. Neither 

 can he undertake to return, or to correspond with 

 the writers of, rejected manuscripts intended for 

 this or any other part of Nature. No notice is 

 taken of anonymous communications.] 



The Perception of Sound. 



The recent publication of Sir Thomas Wrightson's 

 valuable and extensive investigations on the functions 

 of the various parts of the auditory mechanism has 

 brought inn. prominence a fundamental divergence of 

 opinion as to the place where analysis of the complex 

 sound vibrations occurs and as to the mod,- of vibra- 

 tion of the basilar membrane. The view of Helm- 

 holr/ , be said to !>■ thai mosl generall) accepted 

 \s is well known, this theon slates thai 

 ihc basilar membrane responds l>\ resonance in 

 diffen 1 the 1 omponent \\ a\ es o\ the com- 



plex, .in., .', ,,\ these components gives rise to 



its own ,,, ,,,,' arriving at the brain. The 



analysis take in thi cochlea. Sir Thomas Wright- 



son's theoi ceived the powerful support 



of Prof. Keith, ,1, u the basilar membrane as a 



whole follow- in its v . rm thai of the complex, 



that the form oi rapound wave is 



transferred to tin -.1 that eo analysis 



takes place until tin l,i ain 1 reached. 



Careful consideration of tin evidence brought for- 

 ward in support of this view has aroused several 

 difficulties in my mind which, I venture to think. 

 require explanation. 



In the- first place, then at certain physiological 

 facts which mala it extremely difficult to accept am 



NO. 2S5> VOL. I02] 



sort of transmission of a complex wave form through 

 a nervi fibre. 'I he work of Keith Lucas and hi- col- 

 leagues has shown that the- process sel going in a 

 nerve-fibre has a definite time-course and magnitude, 

 whatevei l» the way in which it is produced. If a 

 sound-wave i«- enabled to stimulate a nerve-fibre by 

 some- appropriate receptor organ, the nerve process 



will I), the same, however different tin- form of the 



wave. If thi- he true, it implies tin' necessity foi a 

 peripheral analysis, if there he anv analysis at all. 

 A similar difficulty arises in connection with the 

 perception of notes of high pitch. If Sir 

 [nomas Wrightson's theory is correct, the number 

 of impulses passing along the nerve musi be 

 tin- same a- the number of vibrations in the 

 note, or possibly two ot four times the number. 

 The frog's nerve is incapable- of responding to a 

 second stimulus if it arrives less than 2 months of a 

 second after a previous one. It would, therefore, 

 record all raii-s above 500 per second as identical. 

 Doubtless this "refractory period" is shorter in the 

 warm-blooded animal, but it is scarcely likely to be 

 short enough to enable responses to 40,000 per second 

 to be- transmitted in their e-xael form. 



It will be noticed by the physiological readet that 

 Midler's law. which appears to have been firsl put 

 forward by Sir Charles Bell, is involved here. It has 

 been found thai the sensation evoked from any nerve 

 of special s,-nse is identical, whatever the kind of 

 stimulus applied. The peculiar quality of tout li. tasfa . 

 light, and so on; is clue to the way the fibres end in 

 the brain. Further than this in the- way of explana- 

 tion is at present impossible. But are we to suppose 

 that the- auditory nerve is the only exception to this 

 law? What we should naturally expect would be- that 

 activity in one particular fibre, or, perhaps, sel ol 

 fibres, in thi- nerve would be associated with tin- per- 

 ception of one single definite tone, and that the form 

 of tin- stimulus would be a matter of indifference. 

 Tin- theory of Helmholtz presents no obstacles in this 

 respect . 



In the second place, there is a physical question 

 about which there seem- some confusion. Main physio- 

 logists would lie grateful to Lord Rayleigh if be- would 

 nut us right here. There is no dispute- as to the 

 impression b\ the- stapes on the liquid of the scala 

 vestibuli of a series of impulses, corresponding in 

 wave form with those air vibrations received by the 

 membrana tympani. But. with the exception of the 

 fact that the pressure is intensified, I am unable to 

 see 'how these vibrations, when tin \ arrive in the 

 liquid, differ from those- which would be present in 

 the liquid if it were- conducting sound in the ordinary 

 way. Ii appears to be- forgotten sometimes that 

 Iic|uiels could not conduct sound unless the} were both 

 elastic and compressible. But the latter quality is, 



of course. . M-ni.-h small, so that the amplitude of 

 the vibrations is very minute. The actual movement 

 in space of he column of liquid a- a whole, contem- 

 plated b\ tin Wrightson theory, is quite different, 



and, -,i 1. 11 as I can sec-, the inertia of the ma-- would 



make it 1 ssible for the force available to effect 



such move in nts at the rat' ot several thousand per 

 second. 



rhen mother point involved here which 1 con- 



fess to an inability to understand. When the stapes 

 pushes in th. membrane- of tin- fenestra oyali-, ih. 



movement ol tin- liauid shows itself simultaneously 

 i.\ a Drotrusion of tin- fenestra rotunda. Now the 

 basilar membrane forms part of a partition between 

 the two columns of liauid in tin scala v< stibuli and 



tin- -e-ala i \ in n.ani. If Ihes, columns were not ron- 

 nected at hi aoex of tin- cochlea, it is clear that the- 

 pushing in of the stapes must cause- a bulging of tin 



