814 



THE ORGANS OF SPECIAL SENSE. 



FIG. 430. Circumvallate papillae of tongue 

 of rabbit, showing position of taste-goblets. 

 (Stohr.) a. Duct of gland, d. Serous gland, g. 

 Taste-buds. I, Primary septa, and I', second- 

 ary septa, of papilla, n. Medullated nerve. 

 M. Muscular fibres. 



is transverse. Projecting from their apices are numerous filiform processes or 

 secondary papillae ; these are of a whitish tint, owing to the thickness and density 



of the epithelium of which they are com- 

 posed, and which has here undergone a 

 peculiar modification, the cells having be- 

 come cornified and elongated into dense, 

 imbricated, brush-like processes. They con 

 tain also a number of elastic fibres, which 

 render them firmer and more elastic than 

 the papillae of mucous membrane generally. 

 /Simple papilla, similar to those of the 

 skin, cover the whole of the mucous mem- 

 brane of the tongue, as well as the larger 

 papillae. They consist of closely set, micro- 

 scopic elevations of the corium, containing 

 a papillary loop, covered by a layer of epi- 

 thelium. 



/Structure of the Papillae. The papillae 

 apparently resemble in structure those of 

 the cutis, consisting of a cone-shaped pro- 

 jection of connective tissue, covered with a 

 thick layer of squamous epithelium, and 

 contain one or more capillary loops, amongst 

 which nerves are distributed in great abundance. If the epithelium is removed, 

 it will be found that they are not simple elevations like the papillae of the 

 skin, for the surface of each is studded with minute conical processes of the 

 mucous membrane, which form secondary papillae (Todd and Bowman). In 

 the papillae circumvallatae the nerves are numerous and of large size ; in the 

 papillae fungiformes they are also numerous, and terminate in a plexiform net- 

 work, from which brush-like branches proceed ; in the papillae filiformes their 

 mode of termination is uncertain. Buried in the epidermis of the papillae circum- 

 vallatae, and in some of the fungiformes, are certain peculiar bodies, called taste-buds. 1 

 They are flask-like in shape, their broad base 

 resting on the corium, and their neck opening by 

 an orifice, the gustatory pore, between the cells 

 of the epithelium. They are formed by two kinds 

 of cells ; supporting cells and gustatory cells. 

 The supporting cells are mostly arranged like the 

 staves of a cask, and form an outer envelope for 

 the bud. Some, however, are found in the interior 

 of the bud between the gustatory cells. The 

 gustatory cells occupy the central portion of the 

 bud ; they are spindle-shaped, and each possesses 

 a large spherical nucleus near the middle of the 

 cell. The peripheral end of the cell terminates 

 at the gustatory pore in a fine, hair-like filament, 

 the gustatory hair. The central process passes toward the deep extremity of the 

 bud, and there ends in a single or bifurcated varicose filament, which was formerly 

 supposed to be continuous with the terminal fibril of a nerve ; the investigations 

 of Lenhosse'k and others would seem to prove, however, that this is not so, but 

 tli at the nerve-fibrils after losing their medullary sheaths enter the taste-bud, and 

 terminate in a fine extremity between the gustatory cells. Other nerve-fibrils 

 may be seen ramifying between the cortical cells and terminating in fine 

 extremities ; these, however, are believed to be nerves of ordinary sensation, and 

 not gustatory. 



1 These bodies are also found in considerable numbers at the side of the base of the tongue, just 

 in front of the anterior pillars of the fauces, and also on the posterior surface of the epiglottis and 

 anterior surface of the soft palate. 



FIG. 431. Taste-buds, a, Supporting 

 cells. 6. Gustatory cell. 



