MECHANISM OF GUSTATION. 669 



tubes, have shown that the mucous membrane around a papilla has no gusta- 

 tory sensibility, but that different savors can be distinguished when a single 

 papilla is touched (Camerer). 



In Fig. 238, which represents the dorsal surface of the tongue, the large, 

 circumvallate papillae, usually seven to twelve in number, are seen in the 

 form of an inverted V, occupying the base of the tongue. The fungiform 

 papillae are scattered over the surface but are most abundant at the point and 

 near the borders. Both of these varieties of papillae are distinguishable by 

 the naked eye. 



The circumvallate papillae simply are enlarged, fungiform papillae, each 

 one surrounded by a circular ridge, or wall, and covered by small, secondary 



FIQ. 239. Medium-sized circumvallate FIG. 240. Fungiform, filiform, and hemi- 



papilla (Sappey). spherical papillae (Sappey). 



FIG. 239. 1, papilla, the base only being apparent (it is seen that the base is covered with secondary 



papillae) ; 2, groove between the papilla and the surrounding wall : 3, 3, wall of the papilla. 

 FIG. 240. 1, 1, two fungiform papillae covered with secondary papillae ; 2, 2, 2, filiform papillae ; 3, a 

 filiform papilla, the prolongations of which are turned outward ; 4, a filiform papilla with vertical 

 prolongations ; 5, 5. small filiform papillae with the prolongations turned inward ; 6, 6, filiform 

 papillae with striations at their bases ; 7, 7, hemispherical papillae, slightly apparent, situated 

 between the fungiform and the filiform papillae. 



papillae. The fungiform papillae have each a short, thick pedicle and an en- 

 larged, rounded extremity. According to Sappey, one hundred and fifty to 

 two hundred of these can easily be counted. These,' also, present small, sec- 

 ondary papillae on their surface. When the mucous membrane of the tongue 

 is examined with a low magnifying power, particularly after maceration in 

 acetic or in dilute hydrochloric acid, their structure is readily observed. 

 They are abundantly supplied with blood-vessels and nerves. 



Several glandular structures are found beneath the mucous membrane of 

 the tongue. On either side of the frenum, near the point, is a gland about 

 three-quarters of an inch (20 mm.) long and one-third of an inch (8*5 mm.) 

 broad, which has five or six little openings on the under surface of the 

 tongue (Blandin and Nuhn). Near the taste-beakers, are small, racemose 

 glands, which discharge a watery secretion, by minute ducts which open into 

 the grooves within the walls of the circumvallate papillae (Ebner). 



Taste- Beakers. Loven and Schwalbe (1867) described, under this name, 

 peculiar structures which are supposed to be the true organs of taste. They 

 are found on the lateral slopes of the circumvallate papillge and occasionally 

 44 



