162 ANATOMY OF VERTEBRATES. 



of them sink deep into the nucleus. They are connected with 

 each other, with the roots of the vagus, and with those of the 

 spinal accessory by means of large multipolar cells. In the 

 Giraffe the lower roots emerge, like a small e accessory,' from 

 the cervical part of the myelon. 



The main roots of each hypoglossal quit the macromyelon, be- 

 tween the prepyramid and olive, figs. 81, 82, 9, usually in two 

 bundles, which escape, in many Marsupials, by two precondyloid 

 foramina: but in most Mammals the bundles, perforating sepa- 

 rately the dura-mater, pass out by a single precondyloid foramen, 

 and then unite. The nerve is closely connected with the vagus, 

 and contiguous cervical ganglion of the sympathetic, passes 

 between the carotid and jugular, then forward between the basi- 

 hyal and hyoglossus, and is continued into the substance of the 

 geniohyoglossus beneath the tongue to its tip. 



In the Porpoise a small branch of the * ninth ' is distributed to 

 the sphincter muscle of the posterior nostril, before the supply 

 to the muscles of the hyoid and tongue is sent off from the main 

 part of the nerve-trunk, which is relatively small in Delphinidce. 

 In the Giraffe the motor nerve of the tongue is larger in 

 proportion to the body than in the Ox : it is largest in the 

 Pangolins and Ant eaters, in relation to the great length of the 

 tongue, and frequency and extent of its muscular motions. As 

 the size of the ( ninth ' governs that of its special outlet from 

 the skull, the precondyloid foramen indicates that the great ex- 

 tinct tree-uprooting Sloths (Mi/lodon, Megatherium) applied a 

 long flexible prehensile tongue to the plucking off the branches 

 of their prostrated aliment, in a greater degree, even, than is now 

 witnessed in the Giraffe. 1 



Among the connections of the ninth are some with brandies 

 of the superior laryngeal to the sterno-hyoid and sterno-thyroid, 

 associating the movements of the tongue with those of the 

 larynx. 2 In Quadrumana the cervical branch assumes more 

 the characters of the ' descendens noni ' of Anthropotomy, and 

 supplies the additional differentiated muscles of the hyoid. The 

 ninth, like the ( accessory,' is essentially a motor nerve, and I have 

 not seen a distinct ganglionic or dorsal root in any Mammal. 



The last, lowest, or hindmost, of the motory nerves of the 

 head is that which supplies the muscles of the occipital or fourth 

 haemal, or scapular, arch; and the origins of which, fig. 134, 5, 5, 

 in the course of growth of the neck and cervical part of the 



1 For the light which may be derived from both nervous and arterial foramina in 

 the interpretation of fossil bones, see xcv', pp. 37, 57, pis. vi. vii. xvi. fig. 2, c. 



2 A good view of the distribution of the ' ninth' in the Jaguar is given in uv, pi. 

 xxxi. fig. 3, 19. 



