CH. LIIL] 



THE LINGUAL PAPILLAE 



731 



some being conical (simple or compound) and others filiform ; they 

 are covered by a thick layer of epithelium, which is either arranged 

 over them, in an imbricated manner, or is prolonged from their sur- 

 face in the form of fine stiff projections 

 (fig. 533). In carnivora they are devel- 

 oped into horny spines. From their 

 structure, it is likely that these papillae 

 a mechanical and tactile function, 



FIG. 531. Vertical section of a circumvallate papilla 

 of the calf. 1 and 3, Epithelial layers covering it ; 

 2, taste-buds ; 4 and 4', duct of serous gland open- 

 ing out into the pit in which papilla is situated ; 

 5 and 6, nerves ramifying within the papilla. 

 (Engelmann.) 



rather than that of taste; the latter 

 sense is seated especially in the other 

 two varieties of papillae, the circumvallate 

 and the fungiform. 



In the circumvallate papillae of the 

 tongue of man peculiar structures known 

 as taste-buds are found. They are of an 

 oval shape, and consist of a number of 

 closely packed, very narrow and fusi- 

 form, cells (gustatory cells). This central 

 core of gustatory cells is enclosed in a single layer of broader fusi- 

 form cells (encasing cells). The gustatory cells terminate in fine stiff 

 pikes which project on the free surface (fig. 534, a). 



These bodies also occur in considerable numbers in the epithelium 

 of the papilla foliata, which is situated near the root of the tongue 

 in the rabbit, and is composed of a number of closely packed papillae 

 very similar to the circumvallate papillae of man. Taste-buds are also 

 scattered over the posterior third of the tongue and the pharynx, as 

 low as the posterior (laryngeal) surface of the epiglottis. 



The gustatory cells in the interior of the taste-buds are sur- 

 rounded by arborisations of nerve-fibres. 



FIG. 530. Section of a mucous gland 

 from the tongue. A, Opening of 

 the duct on the free surface; C. 

 basement membrane with nuclei ; 

 B, flattened epithelial cells lining 

 duct. The duct divides into several 

 branches, which are convoluted and 

 end blindly, being lined through- 

 out by columnar epithelium. D, 

 lumen of one of the tubuli of the 

 gland. x i0. (Klein and Noble 

 Smith.) 



