THE TONGUE. 449 



which give the papilla the aspect of a fine brush, and may attain a 

 length of as much as 0-5-0-6-0-7 of a line, with a breadth of 0-02-0-028 

 of a line at their base. The superficial layers of this epithelium resemble 

 the epidermic plates in their long resistance to the action of acids and 

 alkalies, and consist, especially the epithelial processes, only of solid 

 horny scales of 0-022 to 0-028 of a line, which frequently form a more 

 solid axis, and of an external cortex composed of overlapping plates, so 

 that the whole mass may, with some justice, be compared to a hair. 



The primary papilla of the p. filiformes contains distinct connective 

 tissue, and a very considerable number of elastic fibrils, which as 10-20 

 wavy threads of 0-0004-0*0008 of a line, penetrate even to the points of 

 the simple papillae, and give to the whole cone and its processes a cer- 

 tain solidity and firmness which are not possessed by the simple papillae of 

 the mucous membrane. A minute artery ramifies in each filiform papilla, 

 in such a manner, that every simple papilla contains a capillary loop of 

 0-004-0-005 of a line, from whose reunion a small vein arises. It is dif- 

 ficult to discover the nerves, on account of the abundant elastic tissue ; 

 and in many papillae they may be sought in vain. In the majority, how- 

 ever, at least at the base of the papillae, they are quite distinct, in the 

 form of one or two delicate trunks, with 510, dark-edged primitive 

 fibrils of 0-002-0-003 of a line, which gradually become finer as they 

 run towards the point. I have been unable to make out with certainty 

 how the nerves terminate, yet everything appeared to indicate the exist- 

 ence of loops, not, however, in the simple papillae, but at their base. In 

 animals these loops are more distinct, as for example, in the calf, where 

 every filiform papilla receives 10-12 primitive fibrils, of 0-002-0-003 of 

 a line, which diminish to 0*001 of a line, and do not enter the simple 

 papillae. 



The papilloe fungiformes consist of a clavate primary papilla, whose 

 entire surface is beset with closely placed, conical, secondary papillae, 

 0-1-0*12 of a line in length, and invested with a simple epithelium, 

 such as is met with elsewhere in the oral cavity, without filiform pro- 

 cesses, or any very horny cells, and which, measured from their points, 

 has a thickness of 0*04-0-05 of a line. The primary papilla contains 

 far less elastic tissue than the papillce filiformes, and it is almost wholly 

 wanting in the secondary papillae ; on the other hand, a network of 

 bundles of connective tissue of 0*002-0-003 of a line in breadth, is 

 very distinct. The vessels present the same arrangement as in the p^ 

 filiformes, only that they are much more numerous ; and as regards the 

 nerves, one or two larger trunks of 0-04-0-08 of a line, enter into 

 every fungiform papilla, together with many minute filaments, which,, 

 spreading out in the form of a brush, and repeatedly anastomosing (see 

 Zeitschrift fur Wiss. Zool., B. IV. Tab. IV.), finally diverge in all direc- 



29 



