TEE MOUTH. 337 



two sections, one vertical and longitudinal, the other transverse, there is 

 seen, under the dorsal mucous membrane, a layer of red fibres, very close in 

 their texture, and very adherent to that membrane. Amongst these fibres, 

 there are some which affect a longitudinal direction, but the majority are 

 vertical or transverse, and all are interlaced in the most intimate manner. 

 It appears as if this layer (the lingualis superficialis of Man) was perfectly 

 independent of the other muscular fibres, whose insertion it receives. It 

 also forms a portion of those which writers have named the intrinsic muscles 

 of the tongue, and which comprise a superior and inferior, a transverse and a 

 vertical lingualis muscle. An attentive examination, however, readily shows that 

 the fibres proper to this submucous layer are continuous with those which, 

 coming from a point situated beyond the tongue, form the muscles named, in 

 consequence, extrinsic, and that they are only the prolongations of these. 

 This division of the tongue into two orders of muscular fasciculi does not, 

 for this reason, possess the importance generally accorded to it. 



Extrinsic muscles. If the muscular fibres of the tongue appear to be one 

 mass in the superior layer just referred to, it is not so when they are 

 followed beyond this layer ; on the contrary, we see them separate from one 

 another, and even admit between them at least in the fixed portion a 

 certain amount of adipose tissue, which is particularly abundant towards the 

 base, where it forms a mass called the fatty nucleus of Baur ; then they 

 collect into fasciculi, or perfectly distinct muscles. 



In Solipeds, these muscles number five pairs ; 1, The stylo- or Kerato- 

 glossus ; 2, The great Tiyo- or basio-glossus ; 3, The genio-glossus ; 4, The 

 small hyo-glossus (the superior lingual of some authorities) ; 5, The pharyngo- 

 glossus 



STYLO-GLOSSUS. 



(Synonym*. The hyo-glossus longus of Percivatt. Kcrato-glosms externus Leyh. 

 The stylo-glossus of Man.) 



This is a very long riband-shaped band, formed of 'bright-red parallel 

 fibres, and extending from the styloid bone, or large branch of the os hyoides, 

 to each side of the free extremity of the tongue. 



It originates on the external surface of the large hyoideal branch, near 

 its inferior extremity, by a very thin aponeurosis ; and terminates near the 

 tip of the tongue in expanding over the inferior surface and borders of the 

 organ, and confounding its fibres with those of the opposite muscle. 



In the fixed portion of the tongue, this muscle responds : outwardly, to 

 the mylo-hyoideus, sublingual gland, lingual nerve, and the Whartonian 

 duct ; inwardly, to the genio-glossus and great hyo-glossus muscles. The 

 who)e of its free portion is covered by the buccal membrane. 



In contracting, this muscle pulls the tongue towards the back of the 

 mouth, and inclines it to one side when acting independently of its fellow 

 on the opposite side (Fig. 149, 1.) 



GREAT HTO-GLOSST7S Or BASIO-GLOSSTJS. 

 (Synonyms. Hyo-glossus brew's Percivall. Hyo-glossus Leyh.~> 



A wide muscle, flattened on both sides, thicker than the preceding, and 

 composed of fibres passing obliquely forward and upward, the longest of which 

 are anterior. 



Its origin occupies the whole side of the body of the os hyoides, from the 

 extremity of the cornu to that of the anterior appendix. Its fibres^ after 



