THE ALIMENTARY TKAGT. 



281 



M. hijoglossKS. The two M2I. hyoglossi arise (see page 66) some 

 distance apart^ and run forwards and towards each other to meet 

 on the ventral surface of the hyoid bone ; they now assume a lon- 

 gitudinal direction, and course forwards parallel to each other until 

 they reach the M. (jenio-glossus (Fig. 182 C). Each muscle now 

 divides to form coarse bundles, which ascend on either side of the 

 M. genio-glossus towards the dor- 

 sum of the tongue. In this course 

 they are encircled by a strong, 

 elastic, connective-tissue sheath. 

 The sheath is incomplete at the 

 hinder end of the J/, gemo-glossvx, 

 where it possesses rounded aper- 

 tures, through which the glosso- 

 pharyngeal nerves [N, N) disap- 

 pear, to be distributed, after a 

 sharp curve backwards, in the 

 substance of the organ. 



The M. genio-glossus arises, in 

 two parts on either side, at the 

 side of the chin. One part (Fig. 

 182 C) is dorsal and median, the 

 other (Fig. 182 G"^) ventral and 

 external. 



The first part, with its felloAV 

 of the opposite side, forms an 

 arched commissure in the form of 

 muscular rings, which decrease in 

 size from before backwards, and so form a pear-shaped mass : the 

 second, external portion, extends backwards, with a slight obliquity, 

 as a thin, fan-like expansion, to the mucous membrane, where it is 

 inserted. This arrangement can easily be seen after dissecting 

 away the sheath (Fig. 1 83 H?/) ; the hindermost fibres curve sharply 

 into the tongue {Hi/^) ; the anterior fibres pass obliquely forwards 

 and blend with the straight fibres of the dorsal portion of the 

 M. genio-gJossns (Fig. 183 Gg). The arcuate fibres of the J/, genio- 

 glossus pass, for the most part, uj)wards and outwards to the tips of 

 the posterior bifid border of the tongue ; in this course they lie as 

 a rale above the M. Jn/oglossns, but here and there the two muscles 

 intermix (Fig. 183 Gg^), and it is by no means easy to separate 

 them. 



Muscles of the tnngrie, seen from tlie ventral 

 siiiface. 



G 



Gi 



// 



H'l 



L 



M 



N 



Median portion of M. genio-glossiis. 



Lateral portion of M. genio-glossus. 



Hyoid. 



M. hyoglossus. 



Ijarynx. 



Mandible. 



Glossopharyngeal nerve. 



