392 



Mr. A. J. Ellis on Musical Chords. ' [June 16, 



I venture to conclude that the typical anatomical arrangement of a ner- 

 vous mechanism is not a cord with two ends — a point of origin and a 

 terminal extremity, but a cord without an end — a continuous circuit. 



The peculiar structure of the caudate nerve-cells, which I have described, 

 renders it, I think, very improbable that these cells are sources of nervous 

 power, while, on the other hand, the structure, mode of growth, and indeed 

 the whole life-history of the rounded ganglion-cells render it very pro- 

 bable that they perform such an office. These two distinct classes of 

 nerve-cells, in connexion with the nervous system, which are very closely 

 related, and probably, through nerve-fibres, structurally continuous, seem 

 to perform very different functions, — the one originating currents, while the 

 other is concerned more particularly with the distribution of these, and of 

 secondary currents induced by them, in very many different directions. A 

 current originating in a ganglion-cell would probably give rise to many 

 induced currents as it traversed a caudate nerve- cell. It seems probable 

 that nerve- currents emanating from the rounded ganglion-cells may be 

 constantly traversing the innumerable circuits in every part of the nervous 

 system, and that nervous actions are due to a disturbance, perhaps a varia- 

 tion in the intensity of the currents, which must immediately result from 

 the slightest change occurring in any part of the nerve-fibre, as well as 

 from any physical or chemical alteration taking place in the nerve-centres, 

 or in peripheral nervous organs. 



XXIII. " On the Physical Constitution and Relations of Musical 

 Chords.^' By Alexander J. Ellis, F.R.S., F.C.P.S.* Received 

 June 8, 1864. 



When the motion of the particles of air follows the law of oscillation of 

 a simple pendulum, the resulting sound may be called a simple tone. The 

 pitch of a simple tone is taken to be the number of double vibrations 

 which the particles of air perform in one second. The greatest elongation 

 of a particle from its position of rest may be termed the extent of the 

 tone. The intensity or loudness is assumed to vary as the square of the 

 extent. The tone heard when a tuning-fork is held before a proper re- 

 sonance-box is simple. The tone of wide covered organ-pipes and of flutes 

 is nearly simple. 



Professor G. S. Ohm has shown mathematically that all musical tones 

 whatever may be considered as the algebraical sum of a number of simple 

 tones of different intensities, having their pitches in the proportion of the 

 numerical series 1, 2, 3, 4, 5, 6, 7, 8, &c. Professor Helmholtz has esta- 

 blished that this mathematical composition corresponds to a fact in nature, 

 that the ear can be taught to hear each one of these simple tones separately, 

 and that the character or quality of the tone depends on the law of the 

 intensity of the constituent simple tones. 



These constituent simple tones will here be termed indifferently partial 

 * The Tables belonging- to this Paper will be found after p. 422. 



