1 78 ANTHROPOLOGY. 



by the epiglottis : the sides are composed of the aryteno-epiglottidean folds 

 of mucous membrane ; and the apex, which is posteriorly notched or bifid, 

 is formed by the appendices of the arytenoid cartilages. The inferior open- 

 ing of the larynx is always free, and nearly a perfect circle, formed by the 

 lower border of the cricoid cartilage, which is connected to and continuous 

 with the trachea. 



Intermediate between these two openings, and nearly midway within the 

 larynx, is a very remarkable slit-like narrowing of its cavity, named the 

 rima glotticUs. This, the seat of the vocal function, is bounded laterally by 

 the chordae vocales. Its form is variable, and depends on muscular action, 

 being subject to change in shape and size during every act of respiration, 

 voice, and speech. Immediately above the true chordae vocales, the larynx 

 presents on each side a lateral dilatation, called the ventricle or sinus of the 

 larynx. This space is bounded by the semilunar folds known as the false 

 or superior chorda? vocales. From each ventricle the mucous membrane is 

 prolonged upwards in a thimble-like form, constituting a pouch, the sacculus 

 laryngis. 



The arteries which supply the larynx are derived from the superior and 

 inferior thyroid, the former a branch of the external carotid, the latter of 

 the subclavian. The laryngeal nerves are four in number, a superior and 

 an inferior on each side. 



PI. 129, ßg. 82, thyroid cartilage ; fig. 33, cricoid do. ; fig. 34, arytenoid 

 do. ; fig. 35, epiglottis ; fig. 36, section of the larynx : \ upper, ^, lower vocal 

 cord; ^, ventricle. Fig. 37, larynx from before: ', os hyoides ; "^^ ligament 

 connecting the os hyoides with the thyroid cartilage ; ', thyroid cartilage ; 

 *, ligament between the thyroid and the cricoid cartilage ; ^, cricoid carti- 

 lage. Fig. 38, larynx from behind : ', glottis and epiglottis ; "' ', ventricles. 



PI. 127, fig. 5 ', transverse and oblique arytenoid muscles. Fig. 8, larynx 

 from the left side, one half of the thyroid cartilage removed : \ posterior 

 crico-arytenoid muscle ; ', lateral do. ; ', thyro-arytenoid muscle ; \ muscles 

 of the epiglottis. 



2. The Trachea. 



The trachea, continuous inferiorly with the larynx, is a tube composed 

 of from sixteen to twenty-six C-shaped cartilaginous rings, open posteriorly. 

 It commences opposite to the fifth cervical vertebra, and descends to about 

 the third dorsal, where it divides into two branches, called bronchi^ one of 

 which passes to each lung, and there again subdivides. The right bronchus, 

 shorter and broader, extends for an inch before it divides into three branches. 

 The left bronchus, about an inch longer, sinks into the lung on the leftside, 

 below the corresponding pulmonary artery, and opposite the fifth dorsal 

 vertebra. The cartilaginous rings determine the shape and diameter of the 

 trachea, but do not lie in immediate contact, being separated and connected 

 by elastic fibrous ligaments, by which the elongation and contraction of the 

 tube are rendered possible. The posterior portion of the trachea corresponding 

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