374 SPECIAL PHYSIOLOGY. 



and are of three kinds, named the filiform, fungiform, and circumval- 

 late papillae. 



The filiform papillae, so called from their thread-like shape, are by 

 far the most numerous ; they are found closely set over the anterior 

 three-fourths of the tongue, being especially well marked along the 

 central part ; at the sides and tip, they become shorter, and are ar- 

 ranged in oblique, or almost transverse parallel ridges, which gradu- 

 ally disappear as they run to the under surface of the organ ; they are 

 of a whitish color, being covered by a dense and thick epithelium, 

 which is divided, at the apices, into a brush of very fine filaments (Fig. 

 70, a). They are set, for the most part, 'with a slight inclination back- 

 Pig. 70. 



Fig. 70. Diagrammatic view of the papillae of the tongue (Kolliker). a, filiform papilla, showing ita 

 vascular core or centre, with its secondary papillae, buried in the thick epithelium, which ends in a brush, 

 of hair-like character, b, fungiforin papilla, with its numerous secondary papilla?, and thin epithelial 

 covering, c, circumvallate papilla, its secondary papillae, and their epithelial covering. 



wards. Their use is mechanical, and they aid in the tactile sense, but 

 not directly in the sense of taste. 



The fungiform papillae, so called because they are expanded at their 

 free extremities, are scattered irregularly over the dorsum of the 

 tongue, chiefly over its anterior half; they are not so numerous as the 

 filiform papillae, but are of larger size ; they are of a deep red color, 

 and are covered by a thin soft epithelium (Fig. 70, b). The circum- 

 vallate papillae, also red, and covered by a delicate epithelium, are still 

 fewer in number, varying from eight to fifteen, but they are the largest 

 in size. Each is placed at the bottom of a cup-shaped depression (Fig. 

 70, c), so as to be encircled by a little furrow or trench, which being 

 itself surrounded by an elevated rim, or diminutive vallum, has given 

 rise to the name circumvallate, applied to these papillae. They occupy 

 the back part of the tongue, forming two principal rows, like the letter 

 V, with its point turned backwards. Numerous large and soft papillae, 

 intermediate in form between the circumvallate and fungiform kinds, 

 are situated behind, and on each side of, the circumvallate papillae ; 

 they pass, towards the borders of the tongue, into irregularly notched 

 and parallel ridges. Further back, these papillae subside, and the 

 mucous membrane becomes smoother and thinner, and is marked by 

 numerous elevations and recesses, corresponding with the lingual mu- 



