324 



FUNCTIONS OF THE NERVOUS SYSTEM. 



and ill the latter animal, Valentin states that the two trunks pass out from the 

 cranium through separate orifices, and that, after their exit, one may be shown 



[Fig. 156. 



The course and distribution of the Hypo-Glossal or Ninth pair of nerves ; the deep-seated nerves ot 

 the neck are also seen; 1, the hypo-glossal nerve; 2, branches communicating with the gustatory nerve ; 

 3, a branch to the origin of the hyoid muscles ; 4, the descendens noni nerve ; 5, the loop formed with the 

 branch from the cervical nerves ; 6, muscular branches to the depressor muscles of the larynx j 7, a 

 filament from the second cervical nerve, and 8, a filament from the third cervical, uniting to form the 

 communicating branch with the loop from the descendens noni; 9, the auricular nerve; 10, the inferior 

 dental nerve ; 11, its mylo-hyoidean branch; 12, the gustatory nerve ; 13, the chorda-tympani passing to 

 the gustatory nerve; 14, the chorda-tympani leaving the gustatory, nerve to join the sub-maxillary 

 ganglion; 15, the sub-maxillary ganglion; 16, filaments of communication with the lingual nerve; 17, 

 the glosso-pharyngeal nerve; 18, the pneumogastric or par vagum nerve; 19, the three upper cervical 

 nerves; 20, the four inferior cervical nerves; 21, the first dorsal nerve; 22, 23, the brachial plexus ; 24, 

 25, the phrenic nerve; 26, the carotid artery; 27, the internal jugular vein.] 



to be sensory, and the other to be motor. Hence, this nerve, which is the 

 lowest of those that originate in the cephalic prolongation of the spinal cord, 

 generally known as the medulla oblongata, approaches very closely in some 

 animals to the regular type of the spinal nerves; and though in Man it still 

 manifests an irregularity, in having only a single root, yet this irregularity is 

 often shared by the first cervical nerve, which also has sometimes an anterior 

 root only. 



419. The Hypoglossal nerve is distributed not merely to the tongue, but to 

 the muscles of the neck which are concerned in the movements of the larynx ; 

 and the purpose of this distribution is probably to associate them in those 

 actions, which are necessary for articulate speech. Though all the motions 

 of the tongue are performed through the medium of this nerve, yet it would 

 appear, from pathological phenomena, to have at least two distinct connec- 

 tions with the nervous centres ; for in many cases of paralysis, the masticatory 

 movements of the tongue are but little affected, when the power of articula- 

 tion is much injured or totally destroyed : and the converse may be occasion- 

 ally noticed. When this nerve is paralyzed on one side, in hemiplegia, it 

 will be generally observed that the tongue, when the patient is directed to put 



