MUCOUS MEMBKAXE OF THE ORAL CAVITY. 515 



with that of the skin at the border of the lips, is more transpa- 

 rent, soft, and extensible, but possesses considerable firmness. It 

 consists, like the thinnest portions of the latter, of a single layer, 

 formed of collagenous tissue with elastic fibres; presenting a great 

 number of papillae, like those of the skin, on its outer surface- 

 generally simple, but sometimes double, or even multiple, and 

 standing so close together that their bases are nearly in contact, 

 and rarely more than their own breadth apart. They average T J^ 

 to 5 'g of an inch in length, and gi^ to ^J^ of an inch in breadth. 

 They consist of a slightly granular homogeneous substance. 



The papillae upon the upper surface of the tongue demand a 

 particular description. The corium is also here attached directly 

 and closely to the subjacent muscular tissue, by a dense layer of 

 collagenous tissue. The lingual papillae are of three kinds: the 

 papillae circumvallatce, the fungiformes, and the filiformes, or conicce. 

 All these project freely ; but there are also other smaller ones, com- 

 pletely buried in the epithelium, over the whole gustatory region 

 of the tongue. 



1. The papilla filiformes, or coriicce, are crowded between the fungi- 

 formes, and are most abundant on the middle of the tongue. They 

 are conical processes, ^g to |- of an inch long, by yju to gV broad, 

 of the corium of the mucous membrane, divided at their extremi- 

 ties into from five to twenty smaller secondary papillae, of T J to 

 ^g of an inch. These are covered by a thick epithelial coat, drawn 

 out into a number of long, thin, fine, and subdivided processes, 

 resembling a fine brush, and sometimes ^ to ^ of an inch long. 

 The whole mass somewhat resembles a hair (Fig. 344), and is liable 

 to be covered with mucedinous fungi. (Fig. 155.) Each filiform 

 papilla has an artery giving a capillary loop to each of the simple 

 papillae upon it.- Nerves also can be found in most, but not all, of 

 them ; there being in the base of the papilla one or two small 

 trunks with five to ten dark-bordered nerve-fibres, becoming finer 

 as they approach the point. They probably terminate in loops. 

 (KoWker.) (Fig. 345.) 



2. The fungiform papiltce abound particularly on the anterior part 

 of the tongue. They consist of a clavate primary papilla,.^ to T 'g 

 of an inch long, to 6 V to j-% of an inch broad, covered with closely 

 placed, conical, secondary papillae, 720 to TITIF of an i n h l n g> anc ^ 

 covered by a simple epithelium, only 3^3 to s^Vo of an inch thick, 

 over their points. (Fig. 346.) The vessels are arranged, as in the 



