3IO ORGANS OF RESPIRATION. 



part of the arytenoid cartilage as far as the cavity between these 

 cartilages, is of the stratified squamous variety, and is provided with 

 connective-tissue ridges and papillae. The mucosa consists of fi- 

 brous connective tissue, contains many elastic fibers, which become 

 larger and more prominent as the deeper layers of the mucosa are 

 approached, and is rather firmly connected with the structures 

 underneath it, but is somewhat more loosely connected in the re- 

 gions supplied with squamous epithelium. The mucosa contains 

 numerous lymphocytes and leucocytes, which now and then, espe- 

 cially in the region of the ventricles, form simple follicles. In it are 

 found branched tubulo-alveolar glands, which may be single or 

 arranged in groups. These are found at the free posterior portion 

 of the epiglottis, in the region of the latter' s point of attachment 

 i. e., in the so-called cushion of the epiglottis. Larger collections 

 of glands are found in the false vocal cords, and on the cartilages 

 of Wrisberg (cuneiform cartilages), which appear almost imbedded 

 in the glandular tissue and in the ventricles. In the remaining 

 parts of the larynx glands are found only at isolated points. The 

 true vocal cords have no glands. The glands of the larynx are 

 of the mucous variety, containing crescents of Gianuzzi. 



The cartilages of the larynx are of the hyaline variety, with the 

 exception of the epiglottis, the cartilages of Santorini (the latter 

 are derivatives of the epiglottis, Goppert), the cuneiform cartilages, 

 the processus vocalis, and a small portion of the thyroid at the 

 points of attachment of the vocal cords, which consist of elastic car- 

 tilage. 



The vascular supply of the larynx is arranged in three super- 

 imposed networks of blood-vessels. The capillaries are very fine, 

 and lie directly beneath the epithelium. The lymphatic network is 

 arranged in two layers, the superficial being very fine and di- 

 rectly beneath the network of blood capillaries. 



The nerves of the laryngeal mucous membrane will be de- 

 scribed in connection with those found in the trachea. 



B. THE TRACHEA. 



The trachea is lined by a stratified ciliated columnar epithelium 

 containing goblet cells and resting on a well-developed basement 

 membrane. The mucosa is rich in elastic tissue. In the super- 

 ficial portion of the mucosa the elastic fibers form dense strarrds, 

 which usually take a longitudinal direction. The deeper layer of 

 the mucosa is more loosely constructed, and passes over into the 

 perichondrium of the semilunar cartilages of the trachea without 

 any sharp line of demarcation. Numerous leucocytes are scattered 

 throughout the mucosa, and are also frequently found in the epi- 

 thelium. Connecting the free ends of the semilunar cartilages, 

 which are of the hyaline variety, are found bundles of nonstriated 

 muscle tissue, the direction of which is nearly transverse. 



