August 8, 1918] 



NATURE 



443 



changes in the velocity of particles of the peri- 

 lymph in different parts, depending on the degree 

 of resistance to be overcome. 



There is an elaborate chapter on the calibration 

 of the cochlea, showing the ratio of the areas of 

 the various membranes concerned, the measure- 

 ments of the cochlea at different portions of its 

 course, and the manner in which these influence 

 the hairlets in their bendings. In simple and 

 compound tones, the movements of the hairlets 

 correspond in time with the crests, crossing points 

 and troughs of the waves. Considering the me- 

 chanism as an engine, the piston is really the 

 basilar membrane, and the movements are com- 

 municated to the membrana tectoria, and through 

 it to the hairlets connected with the hair-cells. At 

 p. 153 the interesting suggestion is made that if 

 it could be proved that a nerve current passed 

 continuously through the points at which the tips of 

 the hairlets impinge on the membrana tectoria, a 

 kind of microphonic action might take place which 

 would modify the conversion of mechanical im- 

 pulses into nervous irritation — that is, the con- 

 version of mechanical into nervous impulses. 



The second part consists of an appendix, in 

 which Prof. Keith gives an historical and critical 

 account of the structure of the ear. The historical 

 portion is especially valuable, showing the develop- 

 ment of knowledge from the time of the anatomists 

 John and Charles Bell onwards. Special mention 

 is made of the contributions of Bowman, who was 

 one of the pioneers in describing the structure of 

 the spiral laminae and basilar membrane and the 

 so-called muscle or ligament. Then followed Corti, 

 Kolliker, Deiters, and Henle, who all investigated 

 Corti 's organ and prepared the way for Helmholtz. 

 That German physiologist, taking the cue from 

 Hensen, formulated the view that the function of 

 the organ was to convert compound into simple 

 pendular vibrations. The organ, according to 

 Helmholtz, was analytic in its function. Although 

 it was difficult, almost impossible, for the anato- 

 mists, from the small dimensions of its parts, to 

 accept this explanation, it was generally admitted 

 by physicists, as it seemed to meet the difficulties 

 of the case. Prof. Keith submits the matter to a 

 rigorous analysis, and draws the conclusion that 

 there are no anatomical structures which serve as 

 resonators in the cochlea. Generally, he applies Sir 

 Thomas Wrightson's explanation with some modi- 

 fications and refinements, and he is unable to 

 follow Helmholtz. In particular, he attaches 

 importance to the connection between the hairs 

 or hairlets of the cells and the tectorial 

 membrane. Each small group of hairs, surrounded 

 by the fibres of the membrana reticularis, fits into 

 a depression on the under surface of the mem- 

 brana tectoria. The basilar membrane, although 

 c onsisting of fibres arranged in parallel lines, can- 

 not differentiate for separate tones, as the fibres 

 are united side by side and cemented together. It 

 cannot, therefore, be the analytic organ, and the 

 anatomist is obliged to pass upwards to the hair- 

 lets and the membrana tectoria. 



The impression one has, after perusing this 

 NO. 2545, VOL. lOl] 



book, is that this study of the cochlea makes the 

 organ complicated and less easy to understand. If 

 analysis takes place in the cochlea, suitable struc- 

 tures must be met with there which physically 

 would suit the purpose ; if analysis does not occur 

 in the cochlea, why should there be such differ- 

 entiation of structure? In other words, how 

 can we account for the elaboration of the 

 basilar membrane, hair-cells, hairlets, and reti- 

 cular and tectorial membranes, when a direct 

 stimulation of nerve-endings would have served 

 the purpose? Then the principle of resonance, in 

 its real application, would still be serviceable, 

 although the structures were of almost inconceiv- 

 ably minute size. The theory of Helmholtz, 

 although it bristles with obvious difficulties, has 

 at all events the merit of simplicity. We must not 

 forget, also, that minute differences in structure 

 may be morphological other than physiological. 

 This, no doubt, cuts both ways, but it does away 

 with the necessity for having a physiological ex- 

 planation of every structure, however minute. 

 The Helmholtz theory does not explain, for 

 example, the cochlea in the bird, and it is not the 

 last word in the discussion. It may be contended, 

 however, that it serves a purpose that is under- 

 standable. The alternative is to relegate the whole 

 matter to a wilderness of anatomical facts, and 

 we may give up all attempts at explanation by the 

 hypothesis that analysis of compound tones — in 

 short, musical analysis — is a function of nerve- 

 cells in the grey matter of the cerebrum, of which 

 we know next to nothing. 



Both authors deserve great credit for a valuable 

 contribution to our knowledge of the subject. The 

 illustrations arc admirable, and there are many 

 new sections prepared by Prof. Keith. The 

 reasoning is lucid and suggestive. J. G. M. 



OVR BOOKSHELF. 



L'Evolution des Plantes. Par Prof. N. Bernard. 



Preface de J. Costantin. Pp. xxxii + 314. 



(Paris: Librairie F^lix Alcan, 1916.) Price 



4.55 francs. 

 Noel Bernard was elected professor of botany at 

 Poitiers in 1908 and died, at the age of thirty-six, 

 in 191 1. Prof. Costantin, in a preface written at 

 the request of Madame Bernard, gives an interest- 

 ing account of the life and work of his old pupil. 

 Bernard was a man of wide culture and consider- 

 able ability, who devoted most of his scientific life 

 to the experimental investigation of the germina- 

 tion of orchids, with special reference to their 

 symbiotic association with fungi. The concluding 

 chapter of this posthumous volume is a reprint of 

 the introduction to his important paper on 

 "L'Evolution dans la symbrose " published in the 

 Annales des sciences naturelles in 1909. 



The book is characterised by conciseness and 

 clearness, qualities which one expects in the writ- 

 ings of French authors. The first part treats of 

 the general laws of evolution, the evolution of the 

 individuq^soma and of sexual reproduction, the 

 idea of ^ecies, the inheritance of characters, 



