1138 



TONGUE. 



which, in injected specimens, the individual 

 loops of capillaries may be seen projecting 

 with great regularity and beauty (B). The 

 fungiform papillae are largest about the centre 

 of the tongue, smallest along the edges, and 

 most numerous at the sides of the tip, but 

 they are liable to the greatest variety in their 

 size and distribution ; I have seen them HO 

 large about the centre of the tongue, as almost 

 to equal in size the circumvallate ; I have seen 

 them so numerous at the tip, as nearly to 

 equal in number the filiform among which 

 they were scattered ; again, in the same 

 region, I have seen them so scanty, that they 

 could hardly be said to exist there.* 



The conical or filiform papillae, the third 

 class, constitute the great mass of the papillary 

 structure; they cover, in a close-set pile, the 

 whole of the anterior two-thirds of the 

 tongue, being limited behind by the circum- 

 vallate, and having the fungiform scattered 

 among them : it is their structure that imparts 

 the rough coriaceous character to the papil- 

 lary surface, and they constitute the fur in the 

 centre. They are altogether smaller, but in 

 length they exceed, at least in the centre, the 

 other two forms, and they exhibit greater di- 

 versity of structure and a more complete ab- 

 sence of typical shape than either of the other 

 varieties. They affect in some situations a 



Fig. 756. 



A filiform papilla taken from the dorsum of a tongue 

 in which the fur was much developed. (Mag. 30 diam.) 



a, imbricated scaly epithelium investing the cylin- 

 drical portion of the papilla ; b, the commence- 

 ment of its breaking up ; c, its separation into its 

 ultimate filamentary processes ; d, the deep layer 

 of epithelium exposed by the removal of the more 

 scaly superficial one. 



* May not these varieties explain the correspond- 

 ing diversities in the acuteness of the sense of taste, 

 which we so often find in different individuals? 



linear arrangement, principally at their con- 

 fines, that is, in front of and around the 

 caliciform papillae, where they are continuous 

 with the elevations that surround these pa- 

 pilla3, of which they are the continuations 

 forwards and outwards, and along the whole 

 free margin of the tongue, except at the tip, 

 where the linear arrangement cannot be traced. 

 In the first-mentioned situation their rows 

 run forwards and outwards, coinciding with 

 the arms of the V-shaped figure that the cir- 

 cumvallate papillae assume ; in the last-men- 

 tioned, they are placed vertically along the 

 sides (fig. 745. i i) : they have been well de- 

 scribed and figured by Scemmering.* Along the 

 centre of the tongue, in the neighbourhood 

 of the median furrow, the conical papillae often 

 assume a cracked and fissured appearance ; 

 but the linear arrangement is less marked here, 

 and the fissures have no determinate direc- 

 tion, but can be made and effaced according 

 to the movements of the tongue. The conical 

 papillae are largest in the neighbourhood of 

 the circumvallate, where they are truncated, 

 and where some of them assume almost a 

 fungiform shape : they are longest about the 

 centre of the tongue, near the median line, 

 and smallest in the anterior part, near the side 

 and tip. The form of the projections of base- 

 ment membrane, on which the epithelium is 



Fig. 757. 



Vertical section of conical papilla. (Mag. 25 diam.~) 



a, basement surface ; b, conical papilla of ordinary- 

 shape; c, more nearly approaching the simple 

 form ; 17, one quite simple ; e, deep cellular layer 

 of epithelium; f, superficial scaly portion; h h, 

 points from which the filamentary prolongations 

 would have passed up. 



placed, constituting the mould of the true 

 papillary structure, is generally something of 

 a cylindrical shape, the top supporting second- 

 ary papillae, or it is conical, the secondary 

 papillae being continued more or less down the 

 sides : or the base is small, and supports a 

 more expanded portion, and thus the conical 

 is seen to pass into the fungiform shape. But 

 it is in the epithelium that the characteristic 

 difference between these and the other papillae 



* Icones Organoruin humanorum gustus et vocis. 

 Francofurti, 1808. 



