824 



STRUCTURE OF THE ORGANS OF TASTE. 



geal nerve. (4) It is uncertain whether the hard palate and the entrance to the 

 larynx are endowed with taste (Di-ielsma). The middle of the tongue is not gustatory. 

 [Tongue Mucous membrane. The structure of the tongue, as a muscular organ covered with 

 mucous membrane, has already been described ( 155). The dorsal surface of the tongue, in 

 front of the blind foramen, is beset with elevations of the mucous membrane, which extend to 

 its tin nud borders. These elevations, or papill, are of three kinds ; filiform, fungiform, 

 and circumvallate. They consist of elevations of the mucous membrane, visible to the naked 

 eye, and covered by stratified squamous epithelium, while the central core of connective-tissue 

 contains blood- and lymph-vessels and nerves. The filiform papillse occur over the whole tongue, 

 and an- smallest and most numerous. They are conical eminences covered by stratified squamous 



Kpithelium. 



Fig. 604. Fig. 605. 



Fig. 604. Longitudinal section of the dorsum of the human tongue. 1, section of two filiform 

 papilla?, with secondary papilla? (2) ; 3, double, 4, single process of epithelium with loose 

 epithelial scales, x 30. Fig. 605. Longitudinal section of the human tongue. 1, second- 

 ary papillae on 2, the fungiform papilla ; 3, base of 2 ; 4, small filiform papilla, x 30. 

 epithelium, and often beset with secondary papilla? (fig. 604). The fungiform papilla occur 

 chiefly over the middle and front part of the tongue, and are not so numerous as the last. They 

 are club-shaped, with a narrow base, and broad expanded rounded head. They also have 

 secondary papillae. They are generally brighter red than the others (fig. 605). The circum- 

 vallate papilla, 8 to 12 in number, diverge from the foramen caecum at the back part of the 



Fig. 606. 



I, Tranverse section of a circumvallate papilla ; W, the papilla ; v lt v the wall in section ; 

 K, K, the circular slit or fossa ; K, K, the taste-bulbs in position ; N, N, the nerves. II, 

 Isolated taste-bulb ; D, supporting or protective cells ; K, under end ; E, free end, open, 

 with the projecting apices of the taste-cells. Ill, Isolated protective cell (d) with a taste- 

 cell (). 



tongue in two rows in the form of a wide V, the open angle of the V being directed forwards, 

 iney are large, with a broad expanded top, and are lodged in a depression of the mucous mem- 

 brane being surrounded by a wall of mucous membrane, and separated from it by a circular 

 trench, into the base of which gland-ducts often open. They have numerous secondary papilla?, 

 and in them are taste-buds, fig. 606, I.] 



