DEGLUTITION. 569 



tongue to the palate, from the tip to the root, raises the os hyoides, 

 the larynx, and, with it, the anterior paries of the pharynx. The 

 same effect is directly induced by the contraction of the mylo-hyoidei, 

 and genio-hyoidei muscles ; which, instead of acting as depressors of 

 the lower jaw, as they do during mastication, take the jaw as their 

 fixed point, and are levators of the os hyoides. The larynx is thus 

 elevated, carried forwards, and meets the bolus to render its passage 

 over the aperture of the larynx shorter, and, therefore, more speedy. 

 To aid this effect, when we make great efforts to swallow, the head is 

 inclined forwards on the thorax. Whilst the os hyoides and the larynx 

 are raised, they approach each other, the upper margin of the thyroid 

 cartilage passing behind the body of the hyoid bone : the epiglottic 

 gland is pushed backward, and the epiglottis is depressed, and inclined 

 backwards and downwards, so as to cover the entrance to the larynx. 

 The cricoid cartilage executes a rotatory motion on the inferior cornua 

 of the thyroid cartilage, which occasions the entrance of the larynx to 

 -become oblique from above to below, and, of course, from before to 

 behind. The bolus thus glides over its surface ; and, forced on by the 

 veil of the palate, and by the constrictors of the pharynx, reaches the 

 oesophagus. 



At one time, it was universally believed, that the epiglottis is the 

 sole agent in preventing substances from passing into the larynx. 

 The experiments of M. Magendie 1 have, however, demonstrated, that 

 this is the combined effect of the motions of the larynx just described, 

 and of the muscles, whose office it is to close the glottis; so that, if 

 the laryngeal and recurrent nerves be divided in an animal, and the epi- 

 glottis be left in a state of integrity, deglutition is rendered extremely 

 difficult; the principal cause, that prevented the introduction of ali- 

 ments into the glottis, having been removed by the section. M. Magen- 

 die, and MM. Trousseau and Belloc 2 refer to cases of individuals, who 

 were totally devoid of epiglottis, and yet swallowed without any diffi- 

 culty, 3 and Magendie remarks, that if, in laryngeal phthisis with destruc- 

 tion of the epiglottis, deglutition be laboriously and imperfectly accom- 

 plished, it is owing to the carious condition of the arytenoid cartilages, 

 and to the lips of the glottis being so much ulcerated as not to be able 

 to close the glottis accurately. Whilst the bolus, then, is passing over 

 the top of the larynx, respiration must be momentarily suspended, 

 owing to closure of the glottis; and if, from distraction of any kind, 

 we attempt to speak, laugh, or breathe, at the moment of deglutition, 

 the glottis opens, the food enters, and cough is excited, which is not 

 appeased, until the cause is removed. This is what is called, in com- 

 mon language, u the food going the wrong way." As soon as the bolus 

 has cleared the glottis, the larynx descends, the epiglottis rises, and 

 the glottis opens to give passage to the air. This is owing to the 

 relaxation of the muscles that had previously raised the larynx and 



1 Memoire sur 1'Usage de 1'Epiglotte dans la Deglutition, Paris, 1813 ; and Precis, &c., i. 67. 



2 A Practical Treatise on Laryngeal Phthisis, &c. &c.; Dr. Warder's translation, p. 84, 

 in Dunglison's American Medical Library, Philad., 1839. 



3 A similar case is given by Targioni, in which neither deglutition nor speech was im- 

 paired; Morgagni, xxviii. 13. 



