TRACHEA. 485 



The Glands of the larynx are, 1. The epiglottic most impro- 

 perly named for it consists merely of a mass of fat, situated be- 

 tween the convexity of the epiglottis and the thyro-hyoid membrane. 

 2. The arytenoid glands, some small granules found in the folds of 

 mucous membrane near the apex of the' arytenoid cartilage. 



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 pneumo- 

 gastric. The two nerves communicate with each other freely ; but 

 the superior laryngeal is distributed principally to the mucous mem- 

 brane at the entrance of the larynx ; the recurrent, to the muscles. 



In children, and in the female, the larynx is less developed than 

 in the adult male ; the thyroid cartilage forms a more obtuse angle, 

 and is less firm : in the male the angle is acute, and the cartilages 

 often converted into bone. 



THE TRACHEA. 



The TRACHEA extends from opposite the fifth cervical vertebra to 

 opposite the third dorsal, where it divides into the two bronchi. The 

 right bronchus larger than the left, passes oif nearly at right angles 

 to the upper part of the corresponding lung. The left descends 

 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 num- 

 ber, and extend for two-thirds around the cylinder of the trachea. 

 They are deficient at the posterior part, where thd tube is completed 

 by fibrous membrane. The last ring has usually a triangular form 

 in front. The rings are connected to each other by a membrane 

 of yellow elastic fibrous tissue, which in the space between the ex- 

 tremities of the cartilages, posteriorly, forms a distinct layer. 



The Longitudinal elastic fibres are situated immediately beneath 

 the mucous membrane on the posterior part of the trachea, and 

 enclose the entire cylinder of the bronchial tubes to their ultimate 

 terminations. 



The Muscular fibres form a thin layer, extending transversely be- 

 tween the extremities of the cartilages.* On the posterior surface 



* I have several times seen a layer of longitudinal muscular fibres superadded to the 

 transverse. G. 



