John Gray McKendrick

“ At the age of puberty the larynx grows rapidly, and the voice of a boy “breaks” in consequence of the lengthening of the cords, generally falling an octave in pitch. A similar change, but very much less in amount, occurs at the same period in the female. At puberty in the female there is an increase of about one-third in the size of the glottis, but it is nearly doubled in the male, and the adult male larynx is about one-third greater than that of the female. ”

“ Physiology of Voice Production.—The vocal cords are tightened by the action of the crico-thyroid, or, as it might Muscular mechanisms. be more appropriately termed, the thyro-cricoid muscle. It stretches the thyro-arytenoid ligaments, the free edges of which, covered by mucous membrane, form the vocal cords. The adductors of the cords are the lateral crico-arytenoids, while the posterior crico-arytenoids are the abductors. The arytenoid muscle brings the cords together. ”

“ The pitch of the oral cavity for a given vowel may be experimentally determined, or an analysis may be made of the curve-forms of vowels on the wax cylinder of the phonograph or the disk of the gramophone. By such an analysis, according to Fourier's theorem, the curve may be resolved into the partials that take part in its formation, and the intensity of those partials may be thus determined. ”

“ Suppose the picture of the larynx to be examined in the small mirror at the back of the throat, an image will be seen as in fig. 4. During calm breathing, the glottis is lance-shaped, between the yellowish white cords. A deep inspiration causes the glottis to open widely, and in favourable circumstances one may look into the trachea. When a sound is to be made, the vocal cords are brought close together, either along their whole length, as in fig. 7, or only along the ligamentous portion, the space between the arytenoids being still open, as in fig. ”

“ Rarely, incomplete unilateral paralysis of the recurrent nerve, or the existence of a tumour on each cord, thus making them unequal in length, may cause a double tone, or diphthongia. Hoarseness is caused by roughness or swelling of the cords. ”

“ Soc. Ed. (1898) ; Phonetische Stud. (1890–92) ; Jl. of Anat. and Phys. (London) , vol. xxxi. p. 23, ibid, vol xxxi. p. 240. Hermann, Phonophotographische Untersuch., Bd. i.–v.; Archiv f. d. ges. Physiol. ”