TRACHEA. 491 



laryngis is directed upwards, sometimes extending as high as the upper 

 border of the thyroid cartilage, and occasionally above that border. When 

 dissected from the interior of the larynx it is found covered by the aryteno- 

 'epiglottideus muscle and a fibrous membrane, which latter is attached to 

 the superior thyro-arytenoid ligament below ; to the epiglottis in front ; 

 and to the upper border of the thyroid cartilage above. If examined from 

 the exterior of the larynx, it will be seen to be covered by the thyro-epi- 

 glottideus muscle. On the surface of its mucous membrane are the open- 

 ings of sixty or seventy small follicular glands, which are situated in the 

 submucous tissue, and give to its external surface a rough and ill-dissected 

 appearance. The secretion from these glands is intended for the lubrica- 

 tion of the chordce vocales, and is directed upon them by two small val- 

 vular folds of mucous membrane, which are situated at the entrance of the 

 sacculus. 



Glands. The bodies known as the glands of the larynx, namely, the 

 epiglottic and the arytenoid, are very improperly named. The former is 

 a mass of areolo-fibrous and adipose tissue, situated in the triangular space 

 between the front surface of the apex of the epiglottis, the hyo-epiglotti- 

 dean and the thyro-hyoidean ligament. The latter is the body which 

 forms a prominence in the aryteno-epiglottidean fold of mucous mem- 

 brane, and has been described among the cartilages as the cuneiform car- 

 tilage. 



Vessels and Nerves. The Arteries of the larynx are derived from the 

 superior and inferior thyroid. The Nerves are the superior laryngeal and 

 recurrent laryngeal ; both branches of the pneumogastric. The two nerves 

 communicate with each other freely ; but the superior laryngeal is distri- 

 buted principally to the mucous membrane at the entrance of the larynx ; 

 the recurrent, to the muscles. 



THE TRACHEA. 



The TRACHEA extends from opposite the fifth cervical vertebra to oppo- 

 site the third dorsal, w^here it divides into the two bronchi. The right 

 bronchus, larger than the left, passes off nearly at right angles to the upper 

 part of the corresponding lung. The left descencTs obliquely, and passes 

 beneath the arch of the aorta, to reach the left lung. 



The Trachea is composed of 



Fibro-cartilaginous rings, 

 Fibrous membrane, 

 Mucous membrane, 

 Longitudinal elastic fibres, 

 Muscular fibres, 

 Glands. 



The Fibro-cartilaginous rings are from fifteen to twenty in number, and 

 extend for two-thirds around the cylinder of the trachea. They are defi- 

 cient at the posterior part, where the tube is completed by fibrous mem- 

 brane. The last ring has usually a triangular form in front. The rings 



avait indique et faitre presenter la meme disposition." Cruveilhier compares its forrr 

 very aptly to a "Phrygian casque," and Morgagni 8 figure, Advers. 1. Epist. Anat. 3. plat* 

 2. fig. 4, has the same appearance. Bu' neither of these anatomists notice the foilicula* 

 glands described by Mr. Hilton. 



