150 DISSECTION OF THE TONGUE. 



already seen ; and by removing on the lower surface, the inferior lingualis 

 and the genio-hyo-glossus. 



The nerves of the tongue are to be dissected on the left half as well as 

 the part will admit ; but a recent specimen would be required to follow 

 them satisfactorily. 



The transversalis muscle (fig. 38, ) forms a horizontal layer in the 

 substance of the tongue from base to apex. The fibres are attached in- 

 ternally to the side of the septum, and are directed thence outwards, the 

 posterior being somewhat curved, to their insertion into the side of the 

 tongue. 



Its fibres are collected into vertical plates, so as to allow the passage 

 between them of the ascending fibres of the genio-hyo-glossus. 



Action. By the contraction of the fibres of these muscles the tongue is 

 made narrower and rounder, and is increased in length. 



The superior lingualis (fig. 37, A , noto-glossus of Zaglas) is a very thin 

 layer of oblique and longitudinal fibres close beneath the submucous tissue 

 on the dorsum of the tongue. Its fibres arise from the frcenum epiglotti- 

 dis, and from the fascia along the middle line ; from this attachment they 

 are directed obliquely outwards, the anterior becoming longitudinal, to the 

 margin of the tongue, at which they end in the fascia. 



Action. Both muscles tend to shorten the tongue; and they will bend 

 the point back and up. 



The inferior lingualis (fig. 38, D ) is much stronger than the preceding, 

 and is placed under the tongue, between the hyo and genio-hyo-glossus. 

 The muscle arises posteriorly from the fascia at the root of the tongue ; 

 and the fibres are collected into a roundish bundle: from its attached sur- 

 face fasciculi are continued vertically through the transverse fibres up- 

 wards to the dorsum; and at the anterior third of the tongue, where the 

 muscle is overlaid by the stylo-glossus, some of the fibres are applied to 

 that muscle and distributed with it. 



Action. Like the upper lingualis this muscle shortens the tongue, and 

 bends the point down and back. 



The mucous membrane is a continuation of that lining the mouth, and 

 is provided with a laminar epithelium. It partly invests the tongue, and 

 is reflected off at different points in the form of folds (p. 146). At the 

 epiglottis are three small glosso-epiglottid folds, connecting this body to 

 the root of the tongue ; the central one of these is called the fraenum of the 

 epiglottis. Like the membrane of the rnouth, it is furnished with numerous 

 glands, and some follicles. 



The follicles are depressions of the mucous membrane, which are sur- 

 rounded by closed capsules in the submucous tissue, like the arrangement 

 in the tonsil: they occupy the dorsum of the tongue between the papillae 

 circumvallalje and the epiglottis, where they form a stratum, close beneath 

 the mucous membrane. 



The glands (lingual) are racemose or compound in structure, similar to 

 those of the lips and cheek, and are placed beneath the mucous membrane 

 on the dorsum of the tongue behind the papilhe vallatre. A few are found 

 in front of the circumvallate papillae, where they project into the muscular 

 substance. Some of their ducts open on the surface; others into the hol- 

 lows around the large papillte, or into the foramen caecum and the depres- 

 sions of the follicles. 



Opposite the papillte vallatae, at the margin of the tongue, is a small 

 cluster of submucous glands. Under the tip of the tongue, on each side 



