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HANDBOOK OF PHYSIOLOGY. 



lage pass tnrough and open upon the mucous surface of the other side. 

 Taste goblets have been found in the epithelium of the posterior surface 

 of the epiglottis, and in several other situations in the laryngeal mucous 

 membrane. 



The Trachea and Bronchi. The trachea extends from the cricoid 

 cartilage, which is on a level with the fifth cervical vertebra, to a point 

 opposite the third dorsal vertebra, where it divides into the two bronchi 





Fig. 202. Section of the trachea, a, Columnar ciliated epithelium; 6 and c, proper structure of 

 the mucous membrane, containing elastic fibres cut across transversely; d, submucuous tissue 

 containing mucous glands, e, separated from the hyaline cartilage, g, by a fine fibrous tissue, /; h, 

 external investment of fine fibrous tissue. (S. K. Alcock.) 



one for each lung (fig. 201). It measures, on an average, four or four- 

 and-a-half inches in length, and from three-quarters of an inch to an 

 inch in diameter, and is essentially a tube of fibro-elastic membrane, 

 within the layers of which are enclosed a series of cartilaginous rings, 

 from sixteen to twenty in number. These rings extend only around 

 the front and sides of the trachea (about two-thirds of its circumfer- 

 ence), and are deficient behind; the interval between their posterior 

 extremities being bridged over by a continuation of the fibrous mem- 



