1830 HUMAN ANATOMY. 



sound produced by moving the normal larynx laterally, and caused by the friction be- 

 tween the somewhat irregular anterior surface of the vertebral column and the posterior 

 border of the thyroid, the corresponding surface of the cricoid, and the lower part of 

 the pharynx, which move together. This normal crepitus disappears in retropharyn- 

 geal abscess, but persists in retrolaryngeal abscess (Allen). It should be remembered 

 that the superior cornua of the thyroid are sometimes found separate from the body. 



The cricoid and, much more rarely, the thyroid and arytenoid cartilages may 

 be the subject oi perichondritis secondary to ulceration (typhoidal, cancerous, syphi- 

 litic, or tuberculous) of the interior of the larynx. In the case of the cricoid it is 

 asserted that the condition may result from the pressure of the posterior aspect of 

 the cartilage against the spine in very debilitated subjects, or from the traumatism 

 caused by the frequent passage of an oesophageal bougie (Pearce Gould). The 

 origin of the inferior constrictor from the cricoid accounts for the pharyngeal spasm 

 and dysphagia said to accompany disease of this cartilage (Gibbs). 



Allen says that the cricoid is relatively more prominent in women than in men, 

 and that it is often the site to which abnormal sensations originating in the pharynx 

 are referred, because in such conditions deglutition is painful, and since the cricoid lies 

 at the lower part of the pharynx, its motions determine a greater amount of distress 

 than do the corresponding motions at any other part of the throat. 



The epiglottis is not infrequently affected by syphilis, and is also, although more 

 rarely, the seat of tuberculous lesions, and may be extensively ulcerated or may become 

 necrotic. The danger of such cases results usually from the accompanying oedema 

 {vide infra), but in rare instances a sloughing and wholly or partially separated epi- 

 glottis may directly occlude the laryngeal aperture. 



Infection originating in disease of the epiglottis may involve the cellulo-adipose 

 tissue between its base and the thyro-hyoid membrane, giving rise to a thyro-hyoid 

 abscess which may extend towards the mouth and project in the groove between the 

 root of the tongue and the epiglottis. Such an abscess may also follow primary 

 infection of either the tongue or the thyroid. It is very apt to cause oedema of the 

 glottis. The condition known by this name may occur in any form of laryngitis, or 

 by extension of inflammation from the mouth, tongue, or pharynx, or as a result 

 of trauma or of wound, scald, or the application of local irritants. It involves the 

 glottis only secondarily. The thin mucous membrane covering the true vocal cords 

 and the arytenoids is so closely applied to them, and the subcutaneous connective 

 tissue is so scanty, that there is no opportunity for much exudation. But in the 

 supraglottidean region the mucosa is thick and the submucosa plentiful, especially 

 over the aryteno-epiglottidean folds, and almost equally so in the ventricles and over 

 the false cords and the posterior surface of the epiglottis. Effusion of serum and 

 sweUing are thus favored and, according to their degree, will produce hoarseness, 

 aphonia, dyspnoea, cyanosis, or positive suffocation. In some cases of oedematous 

 laryngitis the swelling affects chiefly the region below the glottis {subglottic oedema) 

 and causes the same symptoms. This is rarer and is attended by less effusion on 

 account of the relatively closer association of the mucosa and the cricoid cartilage. 



The mucous glands of the larynx which supply the moisture needed in normal 

 phonation are sometimes inflamed as an indirect result of the over-use of the voice, 

 — as in clergymen, costermongers, public speakers, etc. The increased volume of 

 air taken in through the mouth dries up the mucous surface of the larynx, and the 

 effort to compensate for this may result in such irritation of the glands and mucosa 

 as to cause a form of chronic laryngitis, — " clergyman's sore throat." 



The 7'ima glottidis, — the aperture of the glottis, — the narrowest portion of the 

 air-passages, measures a little less than one inch antero-posteriorly in the adult male. 

 Its transverse diameter at its widest portion is about one-third of an inch. In the 

 male before puberty, and in the female, these measurements are about one-fourth 

 less. They are important in reference to the introduction of instruments and the 

 arrest of foreign bodies (vide infra). 



The level of the glottis — i.e., of the true vocal cords — is a little above the 

 middle of the anterior margin of the thyroid cartilage. 



The shape of the aperture varies. It is linear when a high note is produced in 

 speaking or singing, triatigular (with the apex forward, equal sides and a narrow 



