442 



NATURE 



[August 8, 191 8 



touched after sowing-, so that weeds came up; a 

 fourth was also left untouched, but sufficient water 

 was added to provide for all the needs of crop 

 and weeds, and to allow of full crop growth if 

 the water supply were the limiting factor. The 

 largest yield — 48*9 bushels — was obtained from 

 the plot on which weeds were destroyed; next — 

 with 43*3 bushels — came the well-hoed plot — quite 

 an unexpected result, which, however, leads the 

 authors to an interesting discussion ; thirdly came 

 the watered plot with weeds, which yielded ten 

 bushels ; and only a little behind— with 7-4 bushels 

 — came the plot that had received no water. It is 

 thus clear that the effect of weeds is not 

 merely to deprive the crop of water. The authors 

 conclude that it must therefore have deprived the 

 crop of food. We would commend to them the 

 papers of Mr. Spencer Pickering on the effect of 

 one growing plant on another. 



The chapter on cultivation implements gives 

 illustrations and descriptions of types not gener- 

 ally familiar to English students. Disc ploughs 

 and sulky ploughs are known to some, but 

 listers, spading disc harrows, culti-packers, 

 and weeders will be new to most people 

 here. We should like to have seen this 

 section extended to include a wider discussion 

 of the effect of these implements on the soil — a sub- 

 ject on which the authors could give much valuable 

 information. If need be, space could be found by 

 giving up the sections on fertilisers and some of 

 the geological portions of the opening chapters, 

 which, good as they are, need not necessarily 

 come into a book on soil physics. The authors 

 have done useful service in bringing together so 

 much interesting American material. We may 

 hope one day for a book in which the English 

 and European results will be discussed so that 

 we can compare them with those set out here. 



E. J. Russell. 



THE INTERNAL EAR. 

 An Inquiry into the Analytical Mechanism of the 

 Internal Ear. By Sir T. Wrightson, Bart. 

 With, an Appendix on the Anatomy of the Parts 

 concerned by Prof. A. Keith. Pp. xi + 254 + 

 plates ix. (London: Macmillan and Co., Ltd., 

 1918.) Price 125. 6d. net. 



n^HIS volume is a striking example of the co- 

 ■^ operative method in scientific research. The 

 problem is the mechanism and functions of the 

 internal ear, especially of the cochlea, a 

 problem the solution of which has enlisted 

 the attention of physicists, physiologists, and 

 anatomists with more or less success. One asso- 

 ciates with the cochlea the names of Bowman, 

 Corti, and Helmholtz, besides many others, 

 but this is the first occasion when it has 

 been studied by an experienced engineer 

 working alongside a learned anatomist. Sir 

 Thomas Wrightson, since 1876, has been deeply 

 immersed in acoustics, and he has brought to bear 

 on the cochlea much technical knowledge, derived 

 from wide and varied experience as an engineer. 

 NO. 2545, VOL. lOl] 



He has associated with him Prof. Arthur Keith, 

 an anatomist, familiar with structure, fertile in 

 imagination, and skilful in interpretation. It would 

 be difficult to conceive a combination of workers 

 more suitable for the investigation of that remark- 

 able mechanism by which sound-waves act on the 

 ear and affect the terminations, or, rather, the 

 beginnings, of the auditory nerve. 



The work consists of two parts : (i) The first 

 chapters by Sir Thomas Wrightson, dealing with 

 acoustics chiefly from a theoretical point of view, 

 but always linked with our knowledge of the 

 cochlea; and (2) an appendix, subdivided into 

 parts i. and ii., by Prof. Keith (the curator of the 

 museum of the Royal College of Surgeons), dealing 

 with the mechanism of the internal ear, espe- 

 cially of that all-important portion, the organ of 

 Corti, microscopical in detail, and difficult of inter- 

 pretation. From one point of view, the sense of 

 hearing is a modification of the sense, of touch, 

 which in its turn is a sense of pressure. 

 Between the pressures of sound-waves and 

 the nerve terminals there is an elaborate 

 apparatus for receiving these pressures and con- 

 verting them into nervous impulses. Further, 

 sound-waves vary in number, or frequency, in 

 amplitude, and in form, and the intermediate ap- 

 paratus is adapted to the detection of these varia- 

 tions. 



Sir Thomas Wrightson discusses the nature of 

 simple, compound, and differential tones, illus- 

 trating these graphically by tracings taken by an 

 instrument invented by himself called the ohmo- 

 graph, and from these tracings information is ob- 

 tained as to the variations in wave-form, wave- 

 composition, and velocities at different parts of 

 the tracing. A compound wave is resolved into 

 its constituents, each constituent correspond- 

 ing with a simple tone, or simple pendular move- 

 ment, blending with others to form a resultant tone. 

 The various curves cross each other at certain 

 points. In an air-wave these points or crossings 

 indicate points of pressure on the fluid in the 

 cochlea, and ultimately on the nerve terminals. 

 Pressures are indicated on the "cross" and the 

 "trough," and thus a wave form, in a simple 

 pendular movement, shows phases. Each complete 

 sound-movement consists of four phases, and each 

 phase acts against resistance more or less elastic. 

 These views are illustrated by elaborate diagrams, 

 and they may be said to lie at the foundation of the 

 author's theory of the cochlea. There is no neces- 

 sity for calling into play the principle of resonance, 

 and consequently the author entirely abandons the 

 theory of Helmholtz, which was founded on the 

 conception of resonance. It is not in resonance 

 that there is an explanation, but in the detection 

 of variations of pressure. 



By means of Seebeck's siren it is demonstrated 

 that several musical tones may be heard without 

 confusion. Sir Thomas Wrightson applies this 

 principle to the phenomena of beats, and to dif- 

 ferential and summation tones. It is doubtful, 

 however, whether the ear can distinguish between 

 a push and a pull. The author then proceeds to 

 a consideration of the inner ear, especially as to 



