December 2, 1922] 



NA TURE 



737 



I conclude that the critic was so pained by my 

 restricted use of the term " embryo " (as applied 

 to plants) that he failed to read to the end of the 

 chapter ; otherwise he would not have stated that 

 " experiments on plant physiology are not reached 

 until chapters 16 and 17." I agree that it is desirable 

 to introduce plant physiology' at an earlier stage in 

 the course ; but, with the exception of germination 

 (which is introduced in the Easter Term), the ex- 

 periments seldom yield good results in the winter 

 months. The school year begins towards the end 

 of September, and the arrangement of the chapters 

 (as stated in the preface) was based upon this 

 assumption. E. W. Shann. 



Oundle School, November 10. 



I regret that Mr. Shann regards my review of 

 his book as an " attack," and yet more that it calls 

 from him the word " acerbity." The need for brevity 

 compelled, perhaps, a certain bluntness ; and I beg 

 him to accept my assurance that it was solely to 

 my regard for space in your columns that any such 

 bluntness was due. It was from like considerations 

 that I was obliged to refrain from indicating the 

 authority for and adducing evidence in support of 

 some of my criticisms. 



With regard to the telson and biramous appendage 

 I adhere to mv statement. If Mr. Shann will refer 

 to p. 144, § 2 c of Marshall and Hurst (gth edition, 

 1920), he will see that the telson is spoken of as a 

 " region " of which a " segment " is a part. On referring 

 to the passage in my copy of the " Cambridge Natural 

 History " I find that when I first (presumably in 1909) 

 read its discussion of the relative claims of the 

 biramous and foliaceous limb to be regarded as 

 " primitive," I wrote in the margin " All the facts 

 here stated, if taken in the reverse order, support 

 the opposite theory." This is equally true to-day. 

 If Mr. Shann will read H. M. Bernard's " The Apodidae " 

 (Macmillan, 1892) I shall be astonished if he does not 

 abandon the biramous as the " primitive " form of 

 crustacean limb. 



I duly noted that the course was arranged with 

 the view of beginning in the Michaelmas Term ; but 

 as the very next sentence in the preface suggests 

 modification of the order " at the discretion of the 

 teacher," I felt justified in directing attention to the 

 tardy appearance of plant physiology. The fact that 

 some physiological experiments occur as early as 

 chapter 14 does not seriously affect my criticism. 



The Reviewer. 



The Mechanism of the Cochlea. 



If I understand Dr. Perrett's letter in Nature of 

 November II, p. 633, his objection to Yoshii's ex- 

 periments (which would apply equally to those of 

 Wittmaack and Siebenmann) is based on the assump- 

 tion that the intensity of the stimulation of every 

 part of the cochlea must be proportional to the 

 amplitude of the vibration set up in that part. I 

 think this assumption is unwarranted, as the intensity 

 of the sensory impression may vary also with the 

 rapidity and the rate of change of direction of the 

 movement imparted to the cilia of the hair-cells ; 

 i.e. as the total energy of the stimulus, not its ampli- 

 tude only. Even supposing Dr. Perrett's assumption 

 were correct, still Yoshii's deductions are not invali- 

 dated. Take the case in which he found that after 

 prolonged subjection to high-pitched noise the basal 

 portion of the cochlea showed degeneration. He de- 

 duces the logical conclusion that a high-pitched note 



NO. 2770, VOL. I io] 



stimulates the basal portion of the cochlea. It does 

 not matter whether the stimulus thus applied were 

 small as compared with that produced in the apical 

 region by a prolonged low note or not. The apical 

 region remained unaffected because it was not stimu- 

 lated at all. 



I cannot say that my model shows the shifting of 

 the responses according to the intensity of the stimulus 

 that 1 >r. Perrett says it should do, and possibly my 

 knowledge of phvsics is insufficient to enable me to 

 appreciate the reasons which lead him to look for 

 this result. Personally, I have very little faith in 

 the " crucial test " method of solving the problem of , 

 sound perception. The question has already been so 

 long and so keenly debated, and so many " crucial 

 tests " have been applied on both sides of the argu- 

 ment, that one almost begins to doubt the possibility 

 of tone perception at all. 



I have read Sir William Bayliss' letter (p. 632) with 

 great interest. Naturally, it is very gratifying to me 

 to find that my view of the mechanism of the cochlea 

 has the support of so distinguished a physiologist. 

 I am not very sanguine that my model will throw 

 much light on the more refined details which he 

 gives of the working of the cochlea. What the 

 model actually shows is a definite, though not always 

 well-defined, series of responses at different points 

 along the " basilar membrane " for vibrations varying 

 in frequency from about 100 to about 1000 D.V. per 

 sec, tin- higher notes being at the proximal and the 

 lower at the distal end of the scale. More than this 

 I cannot claim for it. The mechanical difficulty of 

 setting up a series of short threads, evenly spaced, 

 evenly graduated in tension, and maintaining their 

 spacing and tension unaltered during and after the 

 processes of fixation, embedding and immersion in 

 fluid, is so great that I have not succeeded so far in 

 attaining anvthing approaching accuracy. 



One need scarcely.- say that so imperfect an appara- 

 tus cannot, in its present state, throw much light on 

 the more recondite points. If on the other hand we 

 concentrate our attention on the more obvious, and 

 more fundamental factors, I think the model does 

 give some help. We recognise in the basilar mem- 

 brane of the cochlea a threefold differentiation of its 

 fibres, for length, tension and mass, and this differ- 

 entiation is progressive, and in the same sense for 

 each factor. We can embody those mechanical 

 factors crudely in the form of a working model, and 

 we get some sort of remote and inaccurate representa- 

 tion of what happens in the cochlea. The effects 

 observed are undoubtedly resonance effects. It fol- 

 lows that the same resonance effects must take place 

 in the cochlea. One cannot understand how Nature 

 could evolve so elaborate a mechanism of resonance 

 as we find in the cochlea, except by means of, and for 

 the purpose of, increasingly accurate analysis of sound. 



G. Wilkinson. 



387 Glossop Road, Sheffield, Nov. 15. 



An Offer of Nature Volumes. 



The writer has been entrusted with the disposal 

 of thirty-three volumes of Nature (unbound, as issued) 

 which their owner wishes to present to some library 

 in the war-devastated area. These consist of vols. 

 50 to 56, 74 to 92, 97 and 98, and 103 to 107. A few 

 parts are missing. Should any reader of Nature 

 know of some one who may be communicated with 

 for this purpose, the information would be gratefully 

 received. M. Gheury de Bray. 



40 Westmount Road, Eltham, S.E.9, 

 November 13. 



