394 THE MUSCLES AND FASCIA 



The Muscle Substance of the Tongue (Figs. 304 and 305). The muscle fibres of the tongue 

 run in various directions. These fibres are divided into two sets Extrinsic and Intrinsic. The 

 Extrinsic muscles of the tongue are those which have their origin external to, and only their 

 terminal fibres contained within, the substance of the organ. They are: the Styloglossus, the 

 Hyoglossus, the Palatoglossus, the Geniohyoglossus, and part of the Superior constrictor of the 

 pharynx (Pharyngoglossus). The Intrinsic muscles are those which are contained entirely 

 within the tongue, and which form the greater part of its muscular structure. 



The tongue consists of symmetrical halves separated from each other in the middle line by 

 a fibrous septum (septum linguae). Each half is composed of muscle fibres arranged in various 

 directions, containing much interposed fat, and supplied by vessels and nerves. Immediately 

 beneath the mucous membrane is a submucous fibrous layer, into which the muscle fibres which 

 terminate in this stratum of the tongue are inserted. Upon removing this, with the mucous 

 membrane, the first stratum of muscle fibres is exposed. This belongs to the group of Intrinsic 

 muscles, and has been named the Superior lingualis (m. loncjitudinalis superior). It consists 

 of a thin layer of oblique and longitudinal fibres which arise from the submucous fibrous layer, 

 close to the epiglottis, and from the fibrous septum, and which pass forward and outward to the 

 edges of the tongue. Between its fibres pass some vertical fibres derived from the Geniohyo- 

 glossus and from the vertical Intrinsic muscle, which will be described later on. 



Beneath this layer is the second stratum of muscle fibres, derived principally from the 

 Extrinsic muscles. In front this stratum is formed by the fibres derived from the Styloglossus, 

 which run along the side of the tongue and which in turn send out two sets of fibres. The first 

 of these two latter sets of fibres extends over the dorsum and runs obliquely forward and inward 

 to the middle line. The second set of fibres goes on to the under surface of the sides of the anterior 

 part of the tongue, and runs between the fibres of the Hyoglossus muscle forward and inward 

 to the middle line. Behind this layer of fibres, derived from the Styloglossus, are fibres derived 

 from the Hyoglossus, assisted by some few fibres of the Palatoglossus. The Hyoglossus, enter- 

 ing the side of the under surface of the tongue, between the Styloglossus and Inferior lingualis, 

 passes around its margin and spreads out into a layer on the dorsum, which occupies the middle 

 third of the organ, and runs almost transversely inward to the septum. It is reenforced by 

 some fibres from the Palatoglossus; other fibres of this muscle pass more deeply and inter- 

 mingle with the next layer. The posterior part of the second layer of the muscle fibres of the 

 tongue is derived from those fibres of the Hyoglossus which arise from the lesser cornu of the 

 hyoid bone, and are here described as a separate muscle the Ghondroglossus. The fibres 

 of this muscle are arranged in a fan-shaped manner, and spread out over the posterior third 

 of the tongue. 



Beneath this layer is the third layer, the great mass of Intrinsic muscles of the tongue, which 

 is intersected at right angles by the terminal fibres of one of the Extrinsic muscles the Genio- 

 hyoglossus. This portion of the tongue is paler in color and softer in texture than that already 

 described, and is sometimes designated the medullary portion in contradistinction to the firmer 

 superficial part, which is termed the cortical portion. The medullary portion consists largely 

 of transverse fibres, the Transverse lingualis, and of vertical fibres, the Vertical lingualis. The 

 Transverse lingualis (m. transversus linguae) forms the largest portion of the third layer of 

 muscle fibres of the tongue. The fibres arise from the median septum, and pass outward to be 

 inserted into the submucous fibrous layer at the sides of the tongue. Intermingled with these trans- 

 verse intrinsic fibres are transverse extrinsic fibres derived from the Palatoglossus and the Superior 

 constrictor of the pharynx. These transverse extrinsic fibres, however, run in the opposite 

 direction, passing inward toward the septum. Intersecting the transverse fibres are a large 

 number of vertical fibres derived partly from the Geniohyoglossus and partly from intrinsic 

 fibres, the Vertical lingualis. The fibres derived from the Geniohyoglossus enter the under 

 surface of the tongue on each side of the median septum from base to apex. They ascend in 

 a radiating manner to the dorsum, being inserted into the submucous fibrous layer covering 

 the tongue on each side of the middle line. The Vertical lingualis (m. verticalis linguae) is 

 found only at the borders of the forepart of the tongue, external to the fibres of the Geniohyo- 

 glossus. Its fibres extend from the upper to the under surface of the organ, and decussate 

 with the fibres of the other muscles, and especially with those of the Transverse lingualis. 



The fourth layer of muscle fibres of the tongue consists partly of extrinsic fibres derived from 

 the Styloglossus, and partly of intrinsic fibres, the Inferior lingualis. At the sides of the under 

 surface of the organ are some fibres derived from the Styloglossus, which, as it runs forward 

 at the side of the tongue, gives off fibres which, passing forward and inward between the fibres 

 of the Hyoglossus, form an inferior oblique stratum which joins in front with the anterior fibres 

 of the Inferior lingualis. The Inferior lingualis (m. longitudinalis inferior) is a longitudinal 

 band, situated on the under surface of the tongue, and extending from the base to the apex of the 

 organ. Behind, some of its fibres are connected with the body of the hyoid bone. It lies between 

 the Hyoglossus and the Geniohyoglossus, and in front of the Hyoglossus it enters into relation 

 with the Styloglossus, with the fibres of which it blends. It is in relation by its under surface 

 with the ranine artery. 



