ORGANS OF THE BODV. 



4G7 



248. 



While the mucous membrane on the under surface of the tongue is 

 quite smooth and destitute of papillae, the dorsum of the organ is covered 

 from the foramen caecum to the tip with innumerable gustatory papillce. 

 Of these, as is well known, there are three species, although between each 

 kind there exist a number of intermediate forms. These three species 

 are named respectively the filiform, fvngiform, and circumvallate. 



The papillce filiformes, s. conicce (fig. 446), are found in by. far the 

 greatest number of all. They consist of a conical base bearing on its 

 apex a number of thin pointed papillae, the whole presenting a tufted 

 appearance. The number of the latter varies from 5 to 15 and upwards. 

 The point most worthy of note here is the high degree of development to 

 which the epithelial layer may attain. Very horny in texture, it presents 

 itself in long filiform and frequently bifid shreds on the end of the 

 papillae, causing the latter to appear considerably increased in length. 

 Together with these, examples of the same kind of papillae are met with 

 whose epithelial covering is very delicate. 



The vascular supply consists 

 of single capillary loops for 

 each of the conical papillae, 

 with one arterial and one 

 venous twig for each group. 

 The mode of termination of 

 the nerves is not yet ascer- 

 tained. The papillae are most 

 strongly developed along the 

 middle of the dorsum of the 

 tongue, decreasing in size near 

 the edes and tip. In these 

 situations they are in many in- 

 stances arranged in rows, en- 

 veloped in a common sheath 

 of epithelium. 



The second form, the pa- 

 pillce fangi formes, s, clavatce 

 (fig. 447), are found scattered 

 over the whole surface of 

 the tongue among the latter 

 variety, but most numerous 

 towards the tip. They are 

 remarkable for their thick coni- 

 cal form and smooth surface, 

 and absence of tufts, together 

 with diminution in the thick- 

 ness of their epithelial coat. 

 They are elevated above the 

 surface of the tongue with a 

 somewhat constricted neck, and 

 terminate above in round and 

 blunted bulbs. The whole surface of the latter (A) is studded with 

 numerous conical accessory papillae (p), which are covered again by 

 the epithelial coating of the tongue (^4, e, B, e). In this species the 



Fig. 446. Two filiform papillae from man, the one (p, 

 left) with, the other (p. right) without epithelium, e, 

 epithelial covering, ending above in lonsr tufted pro- 

 cesses, /; vascular portion of the papilla, with its 

 arterial twig a, and vein v. Copied from Todd and 



