Chap. xxvi 1 1.] ORGANS OF RESPIRATION. 217 



In the lower part of the larynx the mucous mem- 

 brane contains bundles of elastic fibres connected into 

 networks, and running in a longitudinal direction 

 These elastic fibres are found chiefly in the superficial 

 parts of the mucous membrane. In the true vocal 

 cord the mucosa is entirely made up of elastic fibres 

 extending in the direction of the vocal cord. 



285. The deeper part of the mucous membrane is 

 of loose texture, and corresponds to the sub-mucosa : 

 in it are embedded numerous mucous glands, the ducts 

 of which pass through the mucosa and open on the 

 free surface. The alveoli of the glands are of the 

 nature of mucous alveoli, i.e., a considerable lumen 

 lined with a layer of mucous goblet cells. There are, 

 however, also alveoli lined with columnar albuminous 

 cells, and such as have both side by side, as in the 

 case of the sub-lingual gland of the dog. The ciliated 

 epithelium of the surface in some places extends also 

 for a short distance into the duct. The true vocal 

 cords have no mucous glands. 



The blood-vessels terminate as the capillary net- 

 work in the superficial i.e., sub-epithelial layer of the 

 mucosa; where there are papillae i.e., in the epiglottis 

 and true vocal cord these receive a loop of capillary 

 blood-vessels. The lymphatics form superficial networks 

 of fine vessels, and deep submucous networks of large 

 vessels. These are of enormous width and size in the 

 membrane of the anterior surface of the epiglottis. 

 The finer nerves form superficial plexuses of non- 

 medullated fibres. Here, according to Luschka and 

 Boldyrew, there are end bulbs. Taste-buds have 

 been found in the posterior surface of the epiglottis 

 (Verson, Schofield, Davis), and also in the deeper 

 parts of the larynx (Davis). 



286. II. The trachea. The trachea is very 

 similar in structure to the lower part of the larynx, 

 from which it differs merely in possessing the rings 



