OF THE VOICE AND SPEECH. 455 



601. Of the different associations of Muscular actions, which are em- 

 ployed for various purposes in the living body, it would be out of place here 

 to speak ; since these associations depend upon the Nervous rather than upon 

 the muscular system ; and the most important of them have already been con- 

 sidered in detail. It may be mentioned, however, that the aptitude which is 

 acquired by practice, for the performance of particular actions, that were at 

 first accomplished with difficulty, seems to result as much from a change, 

 which the continual repetition of them occasions in the Muscle, as in the 

 habit which the Nervous system acquires, of exciting their performance. 

 Tims almost every person learning to play on a musical instrument, finds a 

 difficulty in causing the two shorter fingers to move independently of each 

 other and of the rest ; this is particularly the case in regard to the ring-finger. 

 Any one may satisfy himself of the difficulty, by laying the palm of the hand 

 flat on a table, and raising one finger after the other, when it will be found, 

 that the ring-finger cannot be lifted without disturbing the rest, evidently 

 from the difficulty of detaching the action of that portion of the extensor 

 commimis digitorum, by which the movement is produced, from that of the 

 remainder of tlje muscle. Yet to the practised musician, the command of the 

 will over all the fingers becomes nearly alike ; and it can scarcely be doubted 

 that some change takes place in the structure of the muscle, which favours the 

 isolated operation of its several divisions. 



CHAPTER VIII. 



OF THE VOICE AND SPEECH, 



1. The Larynx, and its Actions. 



602. THE sounds produced by the organ of Voice constitute the most im- 

 portant means of communication between Man and his fellows ; and the 

 power of speech has, therefore, a primary influence, as well on his physical 

 condition, as on the development of his mental faculties. Hence, although it 

 only depends on one particular application of muscular force, comparable 

 to that by which other volitional or emotional movements are effected, it 

 seems right, in treating of the Physiology of man, to make it an object of 

 special consideration. In order to understand the nature of the Organ of 

 Voice as a generator of Sound, it is requisite to inquire, in the first, instance, 

 into the sources from which sounds at all corresponding to the human voice 

 are elsewhere obtained. It is necessary to bear in mind, that Vocal Sounds, 

 and Speech or Articulate Language, are two things entirely different; and 

 that the former may be produced in great perfection, where there is no ca- 

 pability for the latter. Hence we should at once infer, that the instrument 

 for the production of Vocal Sounds was distinct from that by which these 

 sounds are modified into articulate speech ; and this we easily discover to be 

 the case, the Voice being unquestionably produced in the Larynx, whilst 

 the modifications of it, by which language is formed, are effected for the most 

 part in the Oral cavity. The structure and functions of the former, then, first 

 claim our attention. 



603. It will be remembered that the Windpipe is surmounted by a stout 

 cartilaginous annulus, termed the Cricoid cartilage ; which serves as a founda- 



