:tl ) '/'//A' DIGESTIVE .iri'AKATUS IN MAMM.il.l I. 



orifice. This arrangement is connected with tho presence, at this part of 

 the tongue, of the closwl /)-///</. x. \\liich are more or less voluminous and 

 aggregated, and separated from the muscles by a continuous layer of raee- 

 moso glands. They are composed of a ca^in^ of condensed connective, and u 

 mass of adenoid tissue, which has in its centre a cavity that communicates 

 with the orifice above the follicle, and is lined by the lingual epithelium 

 minus its horny layer. 



4. Vessels and nerves. Tho tongue is supplied with blood by two 

 arteries, the lingual and sublingmtl ; the blood is removed by three large 

 veins, two of which enter the external maxillary, and the third tlic int> nml 

 maxillary vein. The lymphatics constitute a very fine superficial network, 

 whose emergent branches pass to the submaxillary glands. Tho nerves 

 are the liugual, the glosso-pharyngeal, and the great hypo-glossal ; the latter 

 is a motor nerve, ud consequently supplies the muscles ; the others arc 

 exclusively sensitive, and are distributed more particularly to the mucous 

 membrane. 



FUNCTIONS. The tongue serves for the prehension of liquids in all 

 animals, and for solid aliment in the Ox. It concurs, with the jaws, in pro- 

 pelling the substances to be crushed between the molar teeth during masti- 

 cation ; and it is, besides, one of the essential organs of deglutition. It is 

 able to play this important and complex part through the varied movements 

 it can execute in tho interior of the mouth; and the extent of these move- 

 ments demands a moment's notice. They are of two kinds: those which 

 influence only the form of the organ, and those which cause it to submit to 

 various displacements. They result in either compressing it from side to 

 side, above to below, or curving it longitudinally, and even transversely. 

 These movements are principally, but not exclusively, due to the action of 

 the intrinsic fibres ; they are perfectly independent of the movements which. 

 as a whole, produce the total displacement of the tongue. With regard to 

 these latter, they may result in carrying the tongue beyond the mouth, or 

 withdrawing it into that cavity, inclining it to one side, raising it against 

 the palate, depressing it on the floor of the intermaxillary space or, finally, 

 lifting it towards the pharynx. It is worthy of remark that these move- 

 ments do not alone result from the action of the proper lingual muscles 

 above described ; those belonging to the os hyoides, to whicli is attached 

 the lingual appendix, concur also in producing them. But this appendix is 

 not the only organ thus attached to the hyoidcal apparatus ; the larynx ami. 

 through its intermediation, the pharynx, are placed in the same conditions. 

 and are obliged to follow, like the tongue, the movements of the bony frame- 

 work supporting them. 



There consequently results between these three organs a remarkable 

 unity of action, which is readily explained by the part they all take in the 

 one common act of deglutition. . 



5. Soft Palate. (Figs. 148, 152.) 



Preparation. The soft palate is studied: 1, On the antero-posterior and vortical 

 section of the head (fig. 152,; 2. On the ]n>rtioii intended to show tho interior of tho 

 pharynx (see the preparation of this region); X, On the jtortinn n pn - -nti <! in fig. 148, 

 the mode of dissecting which has been radicated at page 333; iu removing tho ninoons 

 membrane nnd gLm<lnlar luyor, tho iihrous membrane and the two intrinsic muscles are 

 exposed. The extrinsic muscles should be studio! with those of the pharynx. 



Situation Form The soft palate (palatum mollc, velum pendulum pain/ i) 

 is suspended like a partition between the mouth and tho pharynx, and by its 



