October 3.1-, 1918 



NATURE 



165 



more impulse s pi i si ( ond. 1 le 

 rightly says we have no experimental evidence thai .1 

 nerve can convey at the utmosl more than 56b im- 

 pulses per second. He quotes the invesi 

 the fate Dr. Keith Lucas,' bul Keith Lucas was care- 

 ful to point oul 1 lli' Conduction ol t h<- Nervi 

 Impulse") that his work had been necessarily con- 

 fined to Hi. motoi nerves of muscles, and was clearh 

 .11 that his results were not transferable to 

 o v nerves, "particularly in the case ol fight and 

 sound." Indeed, on Helmholtz's theory we infer, and 

 are j 1 1 — 1 i 1 "1 * < 1 in the inference, that certain fibres <ii 

 auditory nerve mi- ile of carrying al 



least 18, impulses pet second if we accept thai 



':mii of our range of hearing. 



In S tVrighteon's theory it is necessary to 



ial every hair-cell is capable ol generating, 



fil iducting, at a rate which 



maj vat] From 60 pet second to 80,000 per second. I 

 thai the internal ear will provide psycho- 

 logists with the meet delicate means oi mvastigating 

 ilw manner in which sensory stimuli are produced bj 



Instead of Helmholtz's theorj being in conformity 

 with Mullet's law, and Sii (Thomas VVrightson 's al 

 variance with it, 1 am of opinion thai the opposite is 



31 quence of having adopted the theorj 

 .if resonators, Herrriholtz had to make the further 

 assumption th.it the auditory differed from everj other 



ich as those of touch, taste, and smell 

 in that its fibres were specialised into 15,000 or mori 

 units cir groups, whereas in ordinary sensory nerves 

 mere is no su, h specialisation, everj one of its fibres 

 being capable of serving the same kind of function. 

 Tli.' i.nh exception is the optic nerve, in which Young 

 and Helmholtz postulated at least three kinds of units 



or fihres. The recent investi-.iii.in-; of Dr. F. W. 

 ind of Dr. R. \. Houston tend to 

 prove that there is no need to postulate a functional 

 differentiation in the fibres of the optic nerve, and 

 similarly the VVrightson theory does away with the 

 -inning that the auditory nerve con- 

 tain-. 15,000 sets of fibris. which are functionally 

 distinct. 



No reference was made by Sir Thomas Wrightson 

 t.i experiments which had dinion-.tr.ited that animals 

 subjected to a prolonged repetition of a note of a high 

 vibrational frequency suffer a ''...million at the 

 narrow, proximal or fenestral end of tin- organ of 

 Corti- just tin- area which we maj presume would 

 be affected if the theory of Helmholtz were true. Nor 

 was allusion made to the less certain results obtained 

 at the opposite • nd of the organ bv prolonged repeti- 

 tion of notes of low frequency. From the measure- 

 ments and data which 1 placed before Sir Thomas 

 Wrightson, he estimates that in all stapedial move- 

 -iir.' f.dU simultaneously and equally on 

 its ,,f the basilar membrane, 1. 111 of this I ;nn 

 1 rinced, conceiving that notes of high frequency, 

 espi . iafly where the waves rise sharnlv to their maxi- 

 mum intensity, will fall chiefly on the proximal or 

 narrow end of the basilar membrane, whereas notes 

 of low frequency, rising slowly to theii maxima, will 

 fill chiefly on the distal or wide end of the membrane. 

 If siii h is the case, then it is not necessarj t.. invoke 

 Helmholtz's theory for their explanation. The 

 planation is not a new one, ha nut forward 



by Pn.f. Max Meyer, of the Cntversit) of Missouri, 

 a numb, r of \ ears ago. 



There are also the cases observed bv aural swgeons 

 Where tone-gaps or islands occur in the gamut of 

 hearing'. These cases receive an apparent explanation 

 on the Helmholtz theory. 1 think it will be found 

 that such cases represent defects in the audirorv 



in corn-spoil, In , u -l,]mdii. ss in tin- visual 



on, both sepn - ; . . - not. La tb 



tl, bin in the ■ enti il, 1 th, auditory and 



visual systems. I would diraci particular attention 

 10 a statement madi h Lucas .on the 



last page (p. 102) of tris po mn ■ ,..k on "The 



1 on. In. ii,,u oi the Nervous Impulse": "On the basis 

 ,'t this analysis we have pictw 1 •ml nervous 



m .1- .1 network having different 



refractory periods, communicating ti ions of 



• iii-ni . easily fatigued." \ nel ,-. - 

 having different refract. exact 



mechanism needed 1." the sorting out of 

 of impulses which reach the auditory centres 

 the fibres of the auditorv nerve. Sir Thomas \\ 

 son has shown that, however complex the sound, 1 ich 

 component part is registered bv the hair-cells a 

 complex passes through the inner ear. Keith Lu. 

 speculations open up the possibility of a central 

 machine for assorting tin- impulses according to their 

 time-intervals. 



I, for one, am particularly glad that Prof. Rayliss 

 has taken an interest in this matter, because his 

 knowledge of that borderland which lies between 

 phvsics and physiologv peculiarly tits him to adjudicate 

 on the claims of the Helmholtz and of the Wrightson 

 theories of the internal ear. A. Keith. 



Royal College of Surgeons, 



Lincoln.'s Inn Fields, W.C.2. 



Epidemic Influenza. 



Prof. Hewlett's interesting article in Nature for 

 October 24 may justify the statement of a few facts 

 collected during the last quarter of a century. Deal- 

 ing with the Registrar-General's returns for London 

 and considering twenty deaths per week as epidemic 

 if this number or more is maintained for successive 

 weeks, there have been twenty-eight epidemics since 

 the reassertion of the complaint in 1890. Of thus. 

 there have only been two, in the years 1910 and 

 191 1, with fewer deaths than 100. The only years 

 in the epoch without influenza being epidemic are 

 1896 and 1901. The most serious epidemics since 

 1S90 occurred in 1S91, 1892, and [899-1900, in each 

 of which there were in London upwards of 2000 

 deaths. In recent years th'- most serious epidemic 

 occurred in 1908 with a total of 1001 deaths, but 

 th,- summer and autumn epidemics of the present 

 year bid fair to be at least as severe. 



The two epidemics of the present year differ very 

 materially from all the other epidemics since 1890 

 with respect to the age-death. The Registrar-General 

 has introduced a slight change in the returns from 

 i<)ii, which prevents 40 being uniformly adopted as 

 .,11 age-limit for death. Taking all the epidemics 

 from 1890 to mill 17, the deaths at ages from o to 

 20 years were 12 per cent, of the total number; from 

 20 to 40 or 4,t years, 14 per cent.; and from 40 or 45 

 years and upwards ;- 1 pet cent. These numbers are 

 r in the several epidemics. For the 

 two epidemics bis yeat the deaths for the respective 

 in s, .-I. pet ' 'in. ; 20 to 45 yea 



I's j it : and above 45 years, 26 pei cent. It is 



an interesting problem to account for the diffei 

 introduced in the ages of death in the epidenil 

 -..;.i year. 



Prof. Hewlett refers to th.- dis.-.is.- waning and 

 .ilm.isi disappearing after the epidemi 3. 14, but 



.in examination of the Registrar-G net il's returns 

 will show that the epidemics wen mally severe 



in 1805. 1899, and 1899-1900, and also in u>o8, 

 the deaths in London from a alone exceeding 



NO. l^^J. VOL. I02] 



