206 THE ANATOMY OF THE HORSE. 



hyoid, it becomes inserted into the glossal or spur process of the 

 hyoid bone. 



Action. — To pull forwards the hyoid bone. 



The Lingual Artery (Plate 32). This is a large branch of the sub- 

 maxillary artery, and has already been seen at its origin. It passes 

 under cover of the great hyo-glossus, crossing the small cornu of the 

 hyoid bone. In passing to the root of the tongue, it crosses obliquely 

 forwards and downwards beneath the middle hyo-glossus and the palato- 

 glossus. In the body of the tongue it lies beneath the great hyo-glossus, 

 and in the free portion of the tongue it is internal to the stylo-glossus. 

 In its course it becomes reduced in size by detaching lateral branches, 

 and it terminates at the tip of the tongue by turning inwards and 

 anastomosing on the middle line with the vessel of the opposite side. 

 Like the lingual nerve, the artery is flexuous in the inferior part of the 

 tongue, that it may be adapted, without stretching, to the varying 

 length of the organ. 



The Glossopharyngeal (9th) Nerve (Plate 32). The lingual 

 continuation of this nerve will be found crossing the inner side of the 

 articulation between the great and small cornua of the hyoid bone to 

 reach the base of the tongue. Here it divides into branches for the 

 mucous membrane on the superior third of the tongue. 



Intrinsic Muscles of the Tongue. The muscles of the tongue 

 already dissected which have points of attachment external to the 

 organ constitute what may be called its extrinsic muscles, but the 

 tongue also contains a considerable amount of muscular tissue of 

 which the bundles have no bony or other external attachment, and 

 are thus intrinsic. These are for the most part intimately mixed with 

 fibres of the extrinsic set, as well as with fat and connective-tissue, but 

 it is possible to distinguish among them three sets of fibres, viz., 

 longitudinal, vertical or antero-posterior, and transverse. The first 

 serve to shorten the tongue, the second make it broader and thinner, 

 and the third increase its thickness and diminish its width. 



THE HARD PALATE (FIG. 24). 



The surface of the hard palate is covered by a dense mucous 

 membrane with a stratified squamous epithelium. It is traversed in 

 its entire length by a median raphe, and is crossed from side to side by 

 from eighteen to twenty curved ridges. The concavity of the ridges is 

 directed upwards (towards the root of the tongue). The ridges are 

 sharpest and the interspaces are narrowest at the upper part of the 

 palate. A layer of connective-tissue with numerous veins connects the 

 mucous membrane to the periosteum of the bones forming the basis 

 of the palate. 



