TONGUE. 



[ 770 ] 



TONGUE. 



The papillaa of the mucous membrane at 

 their bases (p, p) are conical, and covered 

 either at the end only, or all over the sur- 

 face with a number of smaller or secondary 

 papillae ; the whole being coated by an epi- 

 thelial investment (e) } terminating in a tuft 



Fig. 751. 



of free filiform processes (/). The inner 

 layers of the epithelium agree in structure 

 with that of the mouth, whilst the outer 

 layers, and especially the epithelium of the 

 processes, resemble rather the scales of the 

 epidermis, in their hardness, small size, and 



Fig. 753. 



Fig. 752. 



Fig. 754. 



Fig. 751. Fungiform papilla, covered by the epithelium 6 on one side, and with the secondary or simple papilla; p. 

 Magnified 35 diameters. 



Fig. 752. The same, with the vessels; the epithelium e represented in outline, a, artery; v, vein; d, capillary 

 loops of the simple papilla ; c, capillaries in the simple papilla) of the mucous membrane at the base of the fun- 

 giform papilla. Magnified 18 diameters. 



Fig. 753. Perpendicular section of a human circumvallate papilla. A, proper papilla ; JB, wall ; a, epithelium ; 

 b b, nerves of the papilla and wall; c, secondary papillae. Magnified 10 diameters. 



Fig. 754. Follicular gland from the root of the human tongue, a, epithelium ; 5, papillae of the mucous mem- 

 brane ; c, areolar coat ; e, cavity ; /, epithelium lining it ; gg, follicles in the thick capsule. Magnified 30 diameters. 



considerable resistance to the action of 

 alkalies and acids. The papillae themselves 

 consist of areolar tissue, with a large num- 

 ber of undulating nuclear fibres, each con- 

 taining a small artery () and vein (v), with 

 intermediate plexus of looped capillaries, 

 and numerous nerve-tubes. 



The fungiform or clavate papillae (fig. 751) 

 are reddish, distributed over the entire sur- 

 face of the tongue, and are very numerous 

 at its point. Each has at its base a club- 

 shaped mucous papilla, and is covered all 

 over with simple or secondary conical pa- 

 pillae (p,p) and a simple epithelial layer (e), 



without filiform processes. The vessels (fig. 

 752) are more numerous, but otherwise re- 

 semble those in the filiform papillae. 



The circumvallate or lenticular papillae 

 (fig. 753) consist of a flattened central pa- 

 pilla (-4), surrounded by an elevated wall or 

 ridge (B). The flat surface is furnished with 

 crowded conical secondary papillae (c), the 

 whole being covered with epithelium (a) 

 free from processes. The wall appears as a 

 simple fold of the mucous membrane, and 

 also exhibits beneath its smooth epithelial 

 coat numerous rows of simple, conical, se- 

 condary papillae. In other respects these 



