THE ORAL CAVITY. 



249 



are sometimes found taste-buds, or taste-goblets, which lie im- 

 bedded in the epithelium and extend through its entire thickness. 

 The circumvallate papilla occupy a definite region on the upper 

 surface of the tongue, and are arranged in two rows, forming 

 almost a right angle, with the apex directed backward and situated 

 just in front of the foramen caecum (Morgagni). These papillae 

 are few in number, about eight to fifteen in all. In shape they 

 are similar to those of the fungiform type, but are much larger 

 (about I or 2 mm. in diameter), and sunk so deeply into the 

 mucous membrane that the latter forms a wall around their sides. 

 Here also the mucosa passes up into the papillae and forms con- 

 nective-tissue papillse of its own at the upper surface, while at the 

 sides it merely adheres to the smooth inner surface of the epithelial 

 layer. Taste-buds are found in the epithelium at the sides of the 

 papillae, and also in that of the ridges surrounding the papillae. At 

 the sides of the human tongue and near its base are the so-called 

 fimbrice lingua. These are irregular folds of mucous membrane, 



Fig. 193. Longitudinal section of foliate papilla of rabbit, showing taste-buds. 



the sides of which also contain taste-buds. In the rabbit they are 

 more regular in structure and consist of parallel folds of mucous 

 membrane thickly dotted with taste-buds, and are termed the foliate 

 papilla. In place of the circumvallate papillae, the guinea-pig pos- 

 sesses structures similar to the foliate papillae of the rabbit. 



Into the depressions in which the circumvallate papillae lie and 

 into those between the folds of the fimbriae linguae open the ducts 

 of numerous serous glands, the glands of v. Ebner (see below). 



The Taste-buds. The gustatory organs in the form of taste- 

 buds are found on the surface of the tongue, principally on 

 the lateral surfaces of the circumvallate papillae and the fimbriae 

 linguae (foliate papillae). They are also occasionally met with in 

 the epithelium of the fungiform papillae and the soft palate, and on 

 the posterior surface of the epiglottis. They always lie imbedded 

 in the epithelium and extend through its entire thickness ; they are 

 ovoid in form, with base downward and the smaller pole at the 



