PHYSIOLOGY, AND PATHOLOGY OF THE CHIMPANZEE. 335 



the interramal space the two muscles are in contact in the mid 

 line. They are inserted into the upper border of the body 

 and part of the great cornu of the hyoid bone. At their sides 

 lie deposits of fat surrounding the sublingual glands (S.L.G), 

 the numerous arteries to these glands, and the large lingual 

 branch of the trigeminal nerve (L.B.T). The latter is seen 

 vanishing under cover of the genio-hyoid muscle. The hypo- 

 glossal nerve (XII) also is seen dividing into branches which pass 

 under the muscles and sublingual glands. When the genio- 

 hyoidei are reflected it is seen that a well-marked bursa, capable 

 of lodging the tip of the index linger, lies between them and the 

 hyoid bone anteriorly and the genio-glossi posteriorly ; and there 

 is a thick fatty septum between the two genio-glossi. The hyo- 

 glossi crossed antero-postei-iorly by the strong, thick, stylo- glossi ; 

 the sublingual glands and the hypoglossal and lingual nerves are 

 further displayed. The former is seen giving two branches to its 

 corresponding genio-hyoid. 



The genio-glossi (text-fig. 32, G.G) are two long, narrow, thick 

 muscles ai-ising from the bottom of the genial fossa. They are 

 sepaiated in the mid line by a comparatively thick deposit of fat, 

 and a considerable interval separates each from the mandible. 

 In that space the entire sublingual gland, the hyoglossus and 

 styloglossus muscles, the lingual and hypoglossal nerves and the 

 lingual artery are seen. The artery emerges from under the 

 hyo-glossus. Some fibres of the genio-glossi reach the hyoid bone 

 under the hyo-glossus. 



The hyo-glossus (text-fig. 32, HY) arises from the lateral part 

 of the body and the whole of the great cornu of the hyoid bone, 

 but the origin from the body does not spread over a half as stated 

 by Gratiolet (22). The fibres pass upwards to be inserted into 

 the side of the posterior half of the tongue under the stylo- 

 glossus. It is not fused with the opposite muscle, but fibres of 

 the thyro-hyoid can be traced into it. A great part is concealed 

 by the stylo-glossus. The relations are very similar to those 

 in Man. 



The stylo-glossas (text-fig. 32, S.G) is i-elatively more powerful 

 than that in Man. It arises by a short, rounded strong tendon from 

 the outer surface of the base of the styloid process. It describes a 

 curve as in Man, and its volume increases greatly as it is traced 

 forwards. It gains an attachment to the side of the tongue from 

 the level of the outer border of the hyo-glossus behind to nearly the 

 apex of the tongue in front. It covers the upper half of the 

 hyo-glossus, and it extends from the side of the tongue above to 

 the outer border of the genio-glossus below. The part anterior to 

 hyo-glossus is concealed by the large sublingual gland, with the 

 lingual branch of the trigeminal nerve curving round its posterior 

 pole. The connecting loop between the lingual and hypo-glossal 

 nerves crosses it anteriorly, and Wharton's duct (W.D) crosses it 

 obliquely from above downwards and behind forwards. 



The superior constrictor of the pharynoc is continuous above and 



