CH. LV.] 



THE LINGUAL PAPILLA 



781 



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

 face in the form of fine stiff projections (fig. 481). In carnivora they 

 are developed into horny spines. From their structure, it is likely 

 that these papillae have a mechanical and tactile function, rather 

 than that of taste; the latter 

 sense is seated especially in the 

 other two varieties of papillae, 

 the circumvallate and the fungi- 

 form. 



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 fusiform, cells (gustatory 

 cells). This central core ( of 



gustatory Cells IS enclosed in a 



single layer of broader fusiform 



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



which project on the free surface (fig. 482, a). 



Taste -buds are also scattered over the posterior third of the 

 tongue, the palate and the pharynx, as low as the posterior (laryngeal) 



FIG. 479. 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 ; 



c 5 and 6, nerves ramifying within the papilla. 

 (Bngelmann.) 



Fio. 480. Surface and section of the fungiform papillae. A. The surface of a fungiform papilla, partially 

 denuded of its epithelium ; p, secondary papillae ; e, epithelium. B. Section of a fungifonn papilla 

 with the blood-vessels injected ; a, artery ; v, vein ; c, capillary loops of similar papillae in the 

 neighbouring structure of the tongue ; d, capillary loops of the secondary papillae ; e, epithelium. 

 (From Kolliker, after Todd and Bowman.) 



surface of the epiglottis. The gustatory cells in the interior of the 

 taste-buds are surrounded by arborisations of nerve-fibres. 



The arrangement of papillae, taste-buds, etc., varies a good deal in different 

 animals. The papilla foliata of the rabbit's tongue consists of a number of closely 

 packed papillae, similar to the circumvallate papillae of man ; this forms a con- 

 venient source for the histological demonstration of taste-buds. 



