522 THE TISSUES. 



with the vessels, from the external carotid plexus; besides which, 

 the ganglion linguale supplies the two smaller pairs of glands, and 

 the facial nerve, probably with the anterior auricular, the parotid. 



The composition and uses of the saliva have already been speci- 

 fied (pp. 209-10). 



2. Mucous Membrane of the Pharynx. 



Only the lower half of the pharynx will be noticed here; the 

 upper half belonging to the respiratory passages. In that part of 

 it through which the food passes, the epithelium is of the com- 

 pound scaly variety, like that of the oral cavity. The corium of 

 the mucous membrane contains much more elastic tissue than that 

 of the mouth, is paler, and presents none but rudimentary papillae. 



The glands in the lower half of the pharynx are, 1, racemose 

 mucous glands, already described (p. 519), in small numbers ; 2, 

 follicular glands especially on the posterior and lateral walls of 

 the pharynx, as far as to the level of the epiglottis ; 3, the tonsils 

 already described (p. 521). The first two kinds of glands are, how- 

 ever, far more abundant on the upper half of the pharynx, as will 

 be shown further on (Chap. XVI.). 



Bloodvessels, lymphatics, and nerves, abound in the mucous 

 membrane of the pharynx. The muscles of the pharynx are the 

 three constrictors,, the stylo-pharyngeus, and the palato-pharyngeus. 



3. Structure of the (Esophagus. 



While the muscular coat of the pharynx is formed of striated 

 muscular fibres alone (the constrictores pharyngis, &c.), that of the 

 oesophagus contains both kinds of fibres. In its upper third, as 

 far as its entrance into the thorax, only the striated muscular fibres 

 are found, arranged in fasciculi ^ J^ to ^ of an inch in diameter, 

 and which sometimes distinctly anastomose. Lower down, the 

 smooth muscular fibres appear, first in the circular (internal) layer ; 

 and then increase while the striated fibres diminish though the 

 latter are found isolated, and extending even to the cardia. (Fi- 

 cinv.s.) 



The mucous membrane is paler than that of the pharynx, and 

 assumes a whitish tint below. It is -^\ to ^g of an inch thick; its 

 compound scaly epithelium being T ^Q to T^O f an i n h thick; and 

 whose epithelial plates, constituting one-half its thickness, may be 

 readily stripped off in large white sheets, after a short maceration. 



