TONGUE. 



1123 



epiglottis. It contains less muscular and more 

 fibrous tissue than any other part of the 

 tongue. 



Such, then, is a general description of the 

 tongue, such are the appearances that pre- 

 sent themselves to the eye, on regarding its ex- 

 ternal surface and configuration. Let us now 

 examine these structures more minutely, and, 

 to facilitate that examination, arrange the parts 

 that contribute to the formation of the organ, 

 according to the office they fulfil, or their 

 absolute nature. 



Regarding the tongue in this light, we find 

 that it may be considered as consisting of 

 three systems, 



1. A bas'is, or system of support. 



2. A muscular system, or system of move- 

 ment. 



3. A tegumentary investment, or system of 

 sensation and protection. 



1. Basis, or framework of the tongue. This 

 consists of the hyoid bone, the hyoglossal 

 membrane or ligament, the median fibrous 

 septum (the cartilaginous lamina of M. Blan- 

 din), and, fourthly, to these may perhaps be 

 added, on account of its density, and its giving 

 attachment to most of the intrinsic muscles, 

 the compact fibrous tissue, or cutis, beneath 

 the mucous membrane. 



Fig. 746. 



Hyoid bone. A. seen from above, and B. in profile. 

 (Natural size). 



a. The hyoid bone (os hyoides, upsiloides, 

 lingualis, lingua), called also the lingual 

 or tongue bone, has received its name from its 

 resemblance to the Greek u ; it is the homo- 

 logue in man of a very complex mechanism 

 in the lower vertebrata, from which circum- 

 stance it is sometimes called the hyoid ap- 

 paratus. It consists of a bony arch, with a 

 curvature nearly approaching a parabola, the 

 convexity being in front ; situated in an 

 almost horizontal position behind and rather 

 below the lower jaw. In the lower ver- 

 tebrata the hyoid bone is connected to the 

 rest of the skeleton by bony media ; in man, 

 by the substitution of a ligament (the stylo- 

 hyoid) for a part of this osseous connection ; 

 it is isolated, and disconnected from all 



the other bones.* It performs the triple 

 office of a basis of the tongue, a point of 

 support to the larynx, and a paint d'appui or 

 fulcrum, by which the contractions of the 

 intrinsic muscles of the tongue and larynx 

 may be impressed on those organs : it may 

 also be looked upon as the first part of that 

 framework (afterwards generally continued 

 by cartilage) which secures the permanent 

 patulence of the respiratory passages. It is 

 retained in its place by muscles and ligaments, 

 which, converging to it from different direc- 

 tions, effectually prevent its displacement : 

 thus it is tied upwards and backwards by the 

 ligament and muscles from the styloid process, 

 in front by the muscles from the chin and 

 lower jaw, below by those from the thyroid 

 cartilage, sternum, and scapula. Placed be- 

 tween the tongue and larynx, it impresses on 

 each the movement of the other, and is the 

 medium by which the motions of these two 

 organs are so intimately associated. 



Relations. Its whole external surface is 

 devoted to muscular insertions, which separate 

 it, anteriorly and laterally, from the cutaneous 

 structures. Behind, it is in relation with the 

 epiglottis, from which it is separated by some 

 dense cellular tissue, and by the thyrohyoid 

 membrane, and with the mucous membrane of 

 the pharynx. 



In man the hyoid bone consists of five 

 pieces, the basis or body, two greater cornua 

 which project backwards from the sides of the 

 body in a direction nearly horizontal but a 

 little upwards, and two lesser cornua, sur- 

 mounting the body and greater cornua at the 

 point of their union. 



The body is quadrilateral, compressed an- 

 tero-posteriorly, curved, and laterally ex- 

 tended. Its anterior surface looks upwards, is 

 con vex, and intersected by two irregular ridges, 

 a vertical and horizontal, which at the point of 

 their union project in a prominent tubercle, 

 which is the analogue in man of an additional 

 element of the hyoid apparatus in the lower 

 animals the true lingual bone (glossohyar) : 

 this tubercle is sometimes bifurcated. The 

 portion above the transverse ridge is directed 

 much more upwards than that below, so that 

 it has sometimes been called the upper sur- 

 face : in that case the portion below is de- 

 scribed as the whole anterior surface, a cir- 

 cumstance which has led to much confusion 

 with regard to the nomenclature of muscular 

 insertions into this bone. The posterior surface 

 is concave, and looks downwards ; it is marked 

 by many little foramina entering the cancellous 

 structure, and is sometimes covered by a syno- 

 vial membrane. The lateral surfaces, small and 

 articular, are connected to the anterior ex- 

 tremities of the greater cornua by a lamina of 

 temporary cartilage, which, however, is seldom 

 completely ossified, and which admits a certain 

 amount of movement between the different 



* In some rare cases this ligament has been 

 ossified, and then the condition of the os hyoides is 

 the same as that found in most quadrupeds, fish, 

 and reptiles. 



4 c 2 



