TONGUE. 



1125 



cutis underlaying them, may be looked upon, 

 in one light, as a part of the framework of the 

 organ. They form a dense and unyielding 

 envelope, tending to preserve its shape and 

 give it firmness and support, and at the same 

 time affording attachment to a great number 

 of its muscular fibres. 



Such, then, is a concise description of the 

 framework of the tongue. The first and last- 

 mentioned elements of it are, doubtless, the 

 most important; but it will be seen, at a 

 future page, that the intrinsic arrangement of 

 the tongue's muscular fibres is such that they 

 mutually support each other, and tend to keep 

 the organ firm and compact, which obviates 

 the necessity of any considerable structures 

 especially destined for that purpose. 



2. The muscular system. Constituting 

 the chief bulk of the tongue, imparting the 

 required consistence to it, performing the ma- 

 jority of its functions prehension, mastica- 

 tion, deglutition, speech, and necessary even 

 to the perfection of taste, the muscular sys- 

 tem of the tongue may be considered the most 

 important of all. 



The muscles of the tongue are of three 

 sorts, and admit of the following arrange- 

 ment : 



a. Intrinsic. 



b. Extrinsic. 



c. Accessory. 



The intrinsic muscles are those which form 

 the substance of the organ, that pass from 

 part to part of it, and that move the tongue 

 on itself. 



The extrinsic (proper) are those that, as 

 well as entering in some degree into the sub- 

 stance of the tongue, pass from it to neigh- 

 bouring fixed points, to which they attach it, 

 and on which they move it. 



The accessory are those which, though not 

 contributing in any degree to the formation 

 of the tongue, nor attached to it, are yet 

 engaged in all its extrinsic movements, acting 

 as coadjutors to those proper extrinsic mus- 

 cles whose direction coincides with theirs. 



Of the two first I shall speak particularly : 

 little more than their enumeration will suffice 

 for the last. 



a. Intrinsic muscles of the tongue. There 

 are three methods of investigating the arrange- 

 ment of the tongue's intrinsic muscular struc- 

 ture : first, by the ordinary method of dissec- 

 tion, or separation ; secondly, by making 

 sections in different planes, and examining 

 the appearance of the cut surfaces ; thirdly, 

 by the microscopic examination of thin sec- 

 tions. The first, which is the oldest, is that 

 by which we gain the least information ; and 

 to its adoption must be attributed the fact that 

 so many of the older anatomists were in the 

 dark on this subject. By it we merely learn 

 the following facts : that certain of the ex- 

 trinsic muscles pass into the substance of 

 the tongue and contribute to certain of 

 the intrinsic ; that the direction of most of 

 the superficial fibres is more or less longitu- 

 dinal ; that the direction of the more deep- 



seated fibres is not longitudinal ; that it is 

 complex, and incapable of demonstration by 

 separation. 



The second method furnishes much more 

 certain information. By making the sections 

 in different planes, we vary the point from 

 which we regard them ; and the section made 

 in one plane corrects, and supplies the defi- 

 ciencies of, the other. The transverse vertical 

 section is the most important; and to this I 

 shall chiefly refer. 



On making a transverse vertical section of a 

 human tongue, at a point just behind the ante- 

 rior free margin of the genioglossus (fig. 747.), 

 the following are the appearances. Imme- 

 diately within the cutis, which is seen to be to- 

 lerably thick, especially at the centre of the dor- 

 sum {Jig. 747. a.), is seen a dark red stratum, 



Fig. 747. 



Transverse vertical section of human tonque just 



behind the free portion. 



a, upper surface, showing the thickness of the 

 cutis there ; b, cortical portion ; c, central portion, 

 where the vertical fibres are seen crossing the 

 transverse ; d, genioglossi muscles ; e e, sub- 

 lingual glands. 



also thick in the last-mentioned situation, 

 thinner at the lateral regions, and again thicker 

 as it curves inwards on each side of the in- 

 ferior surface. This is very dense, and cuts 

 with a perfectly even surface. I shall call it 

 the cortical portion (fig. 747. Z>.). Within this 

 and surrounded by it as by a border, is an 

 area of a more or less oval form, of a paler 

 colour, less dense, and showing a distinctly 

 fibrous character. The fibres appear for the 

 most part transverse (fig. 747. c.}, horizontal 

 in the centre, but curved up a little on each 

 side. They are bounded on all sides by the 

 cortical portion. Entering the centre of the 

 bottom of the section, passing vertically up- 

 wards, crossing the last-mentioned fibres at 

 right angles, and terminating in the superior 

 surface of the cortical portion, are seen the 

 two genioglossi muscles (fig. 747. d.}. These, 

 therefore, constitute a vertical, set of fibres ; 

 but they are not the only vertical fibres ; at 

 each side of them, especially at the inferior 

 portion of the section, other vertical fibres 

 are seen passing upwards and a little inwards, 

 and intersecting the more lateral portions of 



4 c 3 



