VOICE PHYSIOLOGY. 461 



tenoid cartilages together, so that the chink or cleft of the glottis is 

 sufficiently narrow for the air to cause vibration in the thyro-arytenoid 

 muscles, although they may not be in a state of contraction. From 

 these, and other experiments, Bellingeri 1 infers, that the superior laryn- 

 geal nerve is the antagonist of the inferior laryngeal or recurrent, 

 the former producing constriction; the latter dilatation of the glottis. 

 They, however, who affirm, that the distribution of the laryngeal nerves 

 is not the same as that described by M. Magendie, assign different func- 

 tions to the particular nerves. Thus, Mr. Hilton 2 infers from his 

 observations first, that the superior laryngeal is a nerve of sensation; 

 because, independently of the crico-thyroideal nerve, it is distributed 

 exclusively to the mucous membrane, areolar tissue, and glands ; and 

 secondly, that the inferior or recurrent must be the proper motive nerve 

 to the larynx, as it alone supplies all the muscles, which act immediately 

 upon the column of air passing to and from the lungs. Dr. Reid 3 too, 

 concludes from his various experiments ; first, that the superior laryn- 

 geal furnishes one muscle only with motor filaments, the crico-thyroid. 

 Secondly, that the superior laryngeal furnishes all, or nearly all, the 

 sensitive filaments of the larynx, and some of those distributed upon 

 the mucous surface of the pharynx. Thirdly, that the inferior laryn- 

 geal or recurrent furnishes the sensitive filaments to the upper part of 

 the trachea, a few to the mucous surface of the pharynx, and still fewer 

 to the mucous surface of the larynx; and fourthly, that when any 

 irritant is applied to the mucous membrane of the larynx in a healthy 

 state, this does not excite the contraction of the muscles, which move 

 the arytenoid cartilages, by acting directly upon them through the 

 mucous membrane, but the contraction takes place by a reflex action, 

 in the performance of which the superior laryngeal is the sensitive, and 

 the inferior laryngeal the motor nerve. 



It is obvious from this discrepancy amongst observers, that we have 

 yet much to learn before we can pronounce with certainty on the pre- 

 cise function of those nerves. 



Every part of the larynx, with the exception of the inferior liga- 

 ments, may be destroyed, and the voice continue. Bichat split the 

 upper edge of the superior ligaments of the glottis, without its being 

 destroyed ; and the excision of the tops of the arytenoid cartilages had 

 no more effect. Magendie divided with impunity the epiglottis and its 

 muscles : voice was accomplished, until he cut the middle of the arytenoid 

 cartilages or split the thyroid cartilages longitudinally, when he, of 

 course, destroyed the glottis. Lastly, when the larynx is exposed in a 

 living animal, so that the different parts can be seen at the time when 

 voice is accomplished, the superior ligaments, according to Bichat and 

 Magendie, who have performed the experiment, are manifestly uncon- 

 cerned in the function, whilst the inferior vibrate distinctly. These 



1 Ragionamenti, Sperienze, &c., comprovanti 1'Antagonismo Nervoso, &c., Torino, 1833; 

 noticed in Edinb. Med. and Surg. Journal, p. 172, Jan., 1835. 



2 Op. cit, p. 518, and Mr. Cock, on the Crico-Thyroideal Nerve, a branch of the superior 

 laryngeal, ibid., p 313. 



3 Op. cit., p. 145. 



