THE INTRINSIC MUSCLES OF THE TONGUE. 687 



Its fibres are collected into flattened "bundles, so as to allow the fibres in 

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



Action. By the contraction of the fibres of the two muscles the use - 

 tongue is made narrower and rounder, and is increased in length. 



The SUPERIOR LINGUALIS (fig. 242, A) is a very thin layer of Superficial 

 oblique and longitudinal fibres close beneath the submucous tissue lmgualls : 

 on the dorsum of the tongue. Its fibres arise from the fraenum 

 epiglottidis, and from the fibrous tissue 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 submucous fibrous tissue. 



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

 bend the point upwards. 



The INFERIOR LIXGUALIS (fig. 243, D) is much stronger than the Lower 

 preceding, and is placed on the under surface of the tongue, between lin g ualis : 

 the hyo-glossus and genio-glossus. The muscle arises behind from origin ; 

 the fascia at the root of the tongue ; and the fibres are collected into 

 a roundish bundle : from its attached surface fasciculi are continued ending; 

 upwards through the transverse fibres 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 dis- 

 tributed with it. 



Action. This muscle shortens the tongue, and bends the apex use. 

 down wards. 



The intrinsic PERPENDICULAR FIBRES are found near the border Perpendicu- 

 of the fore part of the tongue, and can be seen only in transverse lar muscle : 

 sections. They pass from the submucous tissue of the dorsum 

 downwards and somewhat outwards, decussating with the cortical 

 and transverse fibres, to the under surface. 



Action. By their contraction these fibres flatten and render use. 

 broader the part of the tongue in which they occur. 



Medullary portion of the tongue. The central part of the tongue, Medulla of 

 which is thus named, is paler in colour and softer than the cortex. 

 It is composed mainly of the bundles of the transverse muscle cross- 

 ing the laminje of the genio-glossus internally and the perpendicular 

 fibres externally, together with interspersed fat. 



The mucous membrane of the tongue is a continuation of that lining Mucous 

 the mouth, and is provided with a stratified scaly epithelium. It its epithe-' 

 invests the greater part of the tongue, and is reflected off at different lmm< 

 points in the form of folds. At the epiglottis are three small 

 glosso-epiylottidean folds, connecting this body to the root of the Folds, 

 tongue ; the central one of these is called the frcenum of the epiglottis. 

 It is furnished with numerous glands, and lymphoid crypts and 

 follicles. 



The crypts are depressions of the mucous membrane, which are sur- Lymphoid 

 rounded by lymphoid follicles in the submucous tissue ("the lingual 

 tonsil"), like the arrangement in the tonsil ; they occupy the dorsum 

 of the tongue between the circumvallate papillae and the epiglottis, 

 where they form a stratum close beneath the mucous membrane. 



