MUCOUS COVERING OF THE TONGUE. 497 



tongue. Those which are next in size and still more abundant, 

 are the Papillae Villosse. The Papillae Filiformes fill up the in- 

 tervals of the others, are the smallest, and are found, principally, 

 near the middle of the tongue and at its front extremity. 



Most commonly the central papilla maxima has the largest 

 fossa of any.of that class, and which is designated by the term 

 foramen ccecum. A little behind this foramen there is frequent- 

 ly another, called the same by some anatomists, but not fur- 

 nished with a papilla, into which some mucous follicles discharge 

 their contents: from time to time it has been fallaciously consi- 

 dered as receiving the excretory duct of the thyroid, or of some 

 of the salivary glands. 



The papillae of the tongue, though they vary in their shape 

 and size, have very much the same structure in regard to the 

 abundance of blood vessels and nerves which enter into their 

 composition. When uninjected, and viewed with the naked eye, 

 their surface appears smooth, but when made turgid by injection, 

 they are covered with little asperities or filaments, which seem to 

 be formed principally of blood vessels, having a very tortuous and 

 superficial course; forming loops, or doublings, in projecting on 

 the surface of the papilla, and anastomosing freely with each 

 other.* Besides vessels, there is a soft whitish substance, sup- 

 posed to be nervous, entering into the composition of each fila- 

 ment. The larger papilla? on the back part of the tongue are 

 supplied by the glosso-pharyngeal nerve, and the papillae on its 

 front part by the trigeminus or fifth pair. 



The surface of the tongue between the papilla? maximae and 

 the os hyoides is destitute of papillae, and is covered only by the 

 common mucous membrane of the mouth, having beneath it many 

 muciparous glands, which in different individuals produce promi- 

 nences more or less elevated, and are of a lenticular shape with 

 a diameter of a line or two. Their orifices are very visible, and 

 easily receive a large bristle. 



The Epidermis, which is found upon all other parts of the lining 

 membrane of the mouth, is also continued over the whote upper 

 surface of the tongue, and consequently invests each papilla; it 

 is called there Peri-glottis. It is soft and humid, may be detached, 

 by maceration, and is frequently detached in fevers. On its up- 



* Soemmering, Anat. J. Cloquet. pi. cxix. 

 42* 



