490 SCIENTIFIC THOUGHT. 



indifferent to the stimulus, which it carries in or out like 

 a telegraph wire ; which, whilst acting in every case in 

 the same way, may, according to its terminal connection, 1 

 " deliver messages, ring a bell, explode a mine, decompose 

 water, create or move magnets, produce light, &c. The 

 same with the nerves. The state of irritation is, so far 

 as the isolated nerve-fibre is concerned, everywhere the 

 same, but in accordance with the nature of different 

 parts, be it of the brain or of the external portions 

 of the body, it produces motion, secretion, increase or 

 decrease of blood, of heat in different organs, or lastly, 

 sensations of light, sound," &c. 



The physiology of hearing had its brilliant application 

 in a clearer understanding of the elements of language, 

 of the formation of the vowel sounds, and in the study of 

 the development of music that art which, more than 

 any other, seems founded on definite rules. 2 In analysing 



1 'Tonempfindungen,' p. 222. '''Masters of Medicine" Series, p. 



2 " From the time when Pythag- 168). 

 oras is said to have discovered the i Since the appearance of the last 



arrangement of tones in an octave, 

 by observing that the sounds of the 

 blacksmith's hammer in the forge 

 produce a fourth, a fifth, and an 

 octave, and was then led to obtain 



edition of Helmholtz's great work, 

 of which there exists an excellent 

 English edition with valuable notes, 

 many of the points first investi- 

 gated by Helmholtz have been taken 



harmonic proportion between the j up by other experimentalists as well 



strings of the heptachord, all who 

 investigate musical tones know that, 

 although these are fleeting sensa- 

 tions, they depend physically on 

 numerical relations between various 

 kinds of movements ; but it was 

 Helmholtz, more than any other 

 philosopher, who examined the 

 whole range of the phenomena, 

 physical as well as physiological, 

 and whose work will for generations 

 remain an enduring monument to 

 his genius" (Prof. M'Kendrick in 



the Helmholtz volume of the 47-96. 



as by psychologists. The invention 

 of the phonograph by Edison in 

 1877 gave a great impetus to exact 

 research in the problems of audi- 

 tion, and various facts and theories 

 have been advanced confirming or 

 modifying the views put forward 

 by Helmholtz. On these see the 

 last chapter of Lord Rayleigh's 

 ' Treatise on Sound,' 2nd ed., 1894. 

 On the psychological side see the 

 2nd volume of Prof. Wundt's 

 ' Physiologische Psychologic,' pp. 



