TONGUE 



235 



epiglottis, and a small portion of those on the anterior and lateral fungi- 

 form papillae. These remain in the adult. In the outer half of each bud 

 the cells converge like the segments of a melon, so that their ends are 

 brought together in a small area. This area is at the bottom of a little pore 

 or short canal found among the outermost flat cells of the epithelium. 

 The taste pore opens freely to the surface, but in oblique sections it may 

 appear bridged as in Fig. 225. 

 Within the bud two sorts 

 of elongated cells may be dis- 

 tinguished, namely, supporting 

 cells which are chiefly peripheral, 

 and taste cells which are central. 

 There are also certain cells which 

 lie wholly in the basal part of 

 the bud, and lymphocytes which 

 have entered the bud from be- 

 low are frequently seen among 

 the other cells. The support- 

 ing cells are paler than the 

 gustatory cells, and may be uni- 

 form in diameter or tapering 

 toward their ends; they are 

 sometimes forked or branched below. The taste cells are darker and more 

 slender, being thickened to accommodate the narrow nucleus which is 

 usually near the middle of the cell. At the taste pore these cells end in 

 a stiff refractive process which is a cuticular formation. The processes 

 extend into the deeper part of the pore but do not reach its outlet. 

 These cells are believed to transmit the gustatory stimuli to the nerves 

 which branch about them. To a less extent the nerves are said to ramify 

 around the supporting cells, which perhaps have other functions than 

 their name implies. 



Taste pore. " 



Supporting 

 cells. 



Taste cells. '*- 



Stratified 

 epithelium. """ 



FIG. 225. FROM A VERTICAL SECTION OF A HUMAN 

 FOLIATE PAPILLA. X 330. 



Tunica 

 propria. 



MOUTH AND PHARYNX. 



The lining of the mouth, like the covering of the tongue, consists of 

 epithelium, tunica propria, and submucosa. At the lips, toward the line 

 of transition from skin to mucous membrane, hairs disappear from the 

 skin. The epithelium becomes thicker but more transparent as it crosses 

 the line (Fig. 226). Its outer cells are still cornined, but they are not so 

 flat and compactly placed as in the skin. The deeper cells appear vesicular. 

 Within the mouth, except on the tongue, cornined cells are absent, but 

 granules of the refractive horny substance, keratohyalin, are said to occur in 

 the outer cells, even in the oesophagus. The free surface of the epithelium 



