134 ORGANS OF RESPIRATION, 



tioned, slopes on its superior margin upwards and backwards? 

 the front surfaces of the arytenoid cartilages, in their natural 

 position, are nearly on a line with this slope, or a continuation 

 of it ; the whole may, therefore, be considered in the light of 

 an oblique plane, rising up behind the epiglottis cartilage. By 

 a very slight additional elevation of this plane along with the 

 rotatory motion of the thyroid cartilage upon its lesser cornua, 

 the plane is caused to com* in contact with the posterior face 

 of the epiglottis, and thereby to close the upper opening of the 

 glottis. 



The principal agents in this motion are the thyreo-hyoid mus- 

 cles, the contraction of which, causing the larynx to ascend, the 

 opening of the glottis is brought up behind the epiglottis, and 

 thereby secured from the introduction of food into it. Whether 

 the food be passed from the mouth into the stomach, as in 

 swallowing, or from the stomach into the mouth, as in vomiting, 

 is equally unimportant; and the security is the same, whether 

 the article be small or large, fluid or solid. Several years ago, 

 I dissected a gentleman who had symptoms of sore throat with 

 swelling of the neck, superadded to those of pulmonary con- 

 sumption: during the existence of his sore throat, in addition 

 to the usual difficulty of swallowing, he was frequently affected 

 in the act, with strangulation to an alarming and distressing de- 

 gree. In the dissection, it was found that an abscess, of con 

 siderable extent, existed between the os hyoides and the thyroid 

 cartilage, and involved the thyreo-hyoid muscles. Without 

 knowing at the time the value of this observation, I am now 

 persuaded that the strangulation arose from the inactivity of 

 the thyreo-hyoid muscles. In some ulcerations of the epiglottis 

 cartilage, which I have had an opportunity of seeing, the up- 

 per circular portion, which projects above the root of the tongue, 

 has been lost; if the accident be confined to that extent only, 

 deglutition is not much impaired, because still enough of the 

 epiglottis is left to perform the office assigned to it, as the up- 

 per part is less essential. The cases of its reputed loss by wounds, 

 must be considered as applying themselves to this upper portion 

 only, because a wound low enough to remove the whole body, 

 would cause such a destruction of the rima glottidis, as to 

 produce an embarrassment of respiration, incompatible with 

 life. 



