SECT. 131.] THE TONGUE. 277 



veivd by an uniformly thick epithelial covering. The surrounding 

 ■wall appears a simple elevation of the mucous membrane, and 

 presents, beneath the epithelial covering on its summit, several 

 series of simple conical papillae. There is generally no elastic 

 tissue in these papillae; in other respects, they agree with the fungi- 

 formes, only they are still richer in nerves. 



Each proper papilla circumvallata contains, in its lowermost 

 parts, several nerve-trunks of 005'" to o-o8'" in diameter, which 

 higher up are resolved into a very beautiful plexus, from which 

 the nerves of the simple secondary papillae proceed, radiating in 

 all directions. The other conditions of the circumvallata are the 

 same as in the fungi formes, only the nerve-tubes, even in the 

 trunks, do not measure on an average more than 0*002'", and 

 scarcely more than 0*003'", whilst at the bases of the papillae they 

 are only o*ooi'" to 0*0015'" in diameter. In the walls surrounding 

 these papillae, there are likewise numerous nerves, of which the more 

 intimate distribution appears to be quite the same as in the papillae. 



According to Sappey, the lymphatics of the tongue form a very 

 dense net-work in the mucous membrane, especially of the upper 

 surface, where they surround the individual papillae, and even form 

 a perfect net-work of delicate vessels in the papilla superficial to 

 that of the blood-vessels. 



The papillae of the tongue exhibit manifold variations, among which the 

 following are the most important : 1. The papilla ftUfurmcs may be all un- 

 usually long, 3nd furnished with epithelial processes of very considerable 

 length. That condition of the tongue, which is commonly called 'coated,' 

 chiefly depends upon the luxuriant growth of the epithelial processes of the 

 papilla filiformes, all of which, directed backwards, and apparently lying upon 

 each other, form a special white covering. If the processes become still 

 longer, so that the papilla Jilifomies measure i%" to 2'", a lingua hirsuta or 

 villosa is produced, which is likewise not unfrequently seen in different 

 diseases, and can at length assume forms which make the tongue appear as 

 if it were beset with hairs 4.'" to 6'" long. 2. The filiform papilla may have very 

 small epithelial processes >>/• none at all, and are scarcely distinguishable from 

 the secondary papilla; of the smallerf/nig formes. 3. Thejiliform papilla may 

 not exist as special projections, hit ouried in the common epithelial covering 

 oj the dorsum of the tongue. It occasionally happens, especially in old people, 

 that the tongue, without being coated, presents at particular spots or over 

 larger surfaces, no papillae, but exhibits either a perfectly smooth surface, or 

 only linear processes, which correspond to the usual rows of papillae. Here 

 the epithelium is more developed, and smaller papillae, presenting more the 

 usual form, lie deeply under it. In other instances, the tongue, even when 

 the papilla; are properly developed, may present a smooth surface, caused by 

 the papilla; being glued together by exuberant epithelium, mucus, blood, pus- 

 o.rpuscles, ferment-fungi, mould, etc., which makes the surface perfectly 



