CHAPTEE LIII 



TASTE AND SMELL 



Taste. 



CERTAIN anatomical facts must be studied first in connection with 

 the tongue, the upper surface of which is concerned in the reception 

 of taste stimuli. 



The tongue is a muscular organ covered by mucous membrane. 

 The muscles, which form the greater part of the substance of the 

 tongue (intrinsic muscles) are termed linguales ; and by these, which 

 are attached to the mucous membrane, its smaller and more delicate 

 movements are performed. 



By other muscles (extrinsic muscles), like the genio-hyoglossus, 

 the styloglossus, etc., the tongue is fixed to the surrounding parts; 

 and by these its larger movements are performed. 



Its mucous membrane resembles other mucous membranes in 

 essential points, but contains papillae, peculiar to itself. The tongue 

 is also beset with mucous glands (fig. 530) and lymphoid nodules. 



The lingual papillae are thickly set over the anterior two-thirds 

 of its upper surface, or dorsum (fig. 529), and give to it its character- 

 istic roughness. Three principal varieties may be distinguished, 

 namely, the (1) circumvallate, the (2) fungiform, and the (3) conical 

 and filiform papillae. They are all formed by a projection of the 

 corium of the mucous membrane, covered by stratified epithelium ; 

 they contain special branches of Wood-vessels and nerves. The 

 corium in each kind is studded by microscopic papillae. 



(1.) Circumvallate. These papillae (fig. 531), eight or ten in number, 

 are situate in a V-shaped line at the base of the tongue (1, 1, fig. 529). 

 They are circular elevations, from ^Vth to T Vth of an inch wide (1 to 

 2 mm.), each with a slight central depression, and surrounded by a 

 circular moat, at the outside of which again is a slightly elevated 

 ring or rampart; their walls contain taste-buds. Into the moat 

 that surrounds the central tower, a few little glands (glands of 

 Ebner) open. They form a thin, watery secretion. 



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