ANATOMY IN A NUTSHELL. 417 



of this nerve is by four or five small filaments from the sides of the medulla just 

 below the superficial origin of the tenth nerve. Its deep origin is in the floor 

 of the fourth ventricle in a gray nucleus at the back of the medulla, dorso- 

 lateral to the hypoglossal nucleus. The superficial ami deep origin just given 

 are those of the accessory portion of the nerve. Tin-: superfk i \i. origin of the 

 spinal portion is from the lateral tract of the cord as low down as the sixth cer- 

 vical nerve. The deep origin of the spinal portion may be traced to the 

 medio-lateral tract of the gray matter of the cord. This spinal portion of the 

 nerve passes upward between tin ligamentum denticulatum ami the posterior 

 roots of the spinal nerves to enter the skull through the foramen magnum. It 

 is then directed outward to the jugular foramen where it passes through the 

 middle compartment of this foramen in a common sheath with the pneumogas- 

 tric but separated from it by a fold of arachnoid. While in the cranium it in- 

 n -changes fibers with the accessory portion. After passing out of the foramen 



PLATE CCXXIV. 



SUPERIOR DIVISION OF ,RD. 



'W/Ji / 



NASAL ' 



INFERIOR DIVISION OF RD. 

 TH. 

 OPHTHALMIC VEIN 



OPTIC FORAMEN 



Showing Structurks Passing Through the Sphenoidal Fissure. 



in.- gnum, it passes downward behind the Digastric and Stylo-hyoid muscles to 

 the upper part of the Sterno-cleido-mastoid. It supplies the Sterno-cleido- 

 oid and crosses the post( rior triangle of the neck to the d< ep surface of the 

 Trapezius. The accessory portion, while in the jugular foramen, is connected 

 to the ganglion of the root of the pn< umogastric, and sonic of its fib< rs become 

 B< parated from the spinal portion and pass to the ganglion of the trunk of the 

 pneumogastric from which they p;>ss to the pharyngeal and superior laryngeal 

 branches of the pneumogastric. It supplies the muscles of the soft palate 

 through the pharyngeal branch. Some of the branches are continue. I below 

 die ganglioD of the trunk of the pn< umogastric into the recurrent laryng< ;i! ami 

 cardiac nerves. This is the nerve that is affect ed in spasmodic torticollis. (Plate 



CCXXII). 



LESSON ('Will. 

 The twelfth cranial nerve or hypoglossal is exclusively motor and supplies 



the intrinsic muscles of the tongue and the Genio-hyoid muscle and all the ex- 

 trinsic muscles of the tongue e\c< pt the PalatO-gloSSUS. 'I'm SUPERFICIAL 

 ORIGIN of this nerve arises by tell or fifteen filaments between the pyramidal and 



