DISSECTION OP THE HEAD AND NECK. 193 



3. The Submental Artery is detached at the extremity of the sub- 

 maxillary gland, as the parent artery appears in the intermaxillary 

 space. It has already been seen in the dissection of that space. 



The Occipital Vein. This vein descends from beneath the wing of 

 the atlas, in company with the artery of the same name ; and joins the 

 juguhxr at the posterior edge of the parotid gland, a little above the 

 termination of the submaxillary vein. It is formed by the union of 

 branches corresponding to those of the artery; and, besides these, it 

 receives a branch which comes from the spinal canal by traversing the 

 ring of the atlas, beneath the wing, and another from the subsphenoidal 

 sinus. This last will be exposed at a later stage. 



The 9th Cranial Nerve, also called the Glosso-Pharyngeal (Plate 

 32), issues from the cranium by the posterior part of the foramen lacerum 

 basis cranii. It descends on the guttural pouch, behind the great cornu 

 of the hyoid bone, and under cover of the digastric and stylo-hyoid 

 muscles ; and it here crosses to the inner side of the external carotid 

 artery. Reaching the pharynx, it continues to descend either close 

 behind the posterior edge of the great cornu or under cover of it ; and 

 here it is crossed by the pharyngeal artery, which may pass either over 

 or under it. It next passes within the articulation of the great and 

 small cornua to reach the root of the tongue, where its terminal branches 

 will be seen at a later stage. It gives off the following branches, the 

 first of which will not now be seen : — 



1. The Nerve of Jacohson, given off from Andersch's ganglion — a 

 minute ganglion placed on the nerve where it issues from the cranium. 

 Jacobson's nerve enters a minute foramen in the petrous temporal bone, 

 and is distributed to the tympanum. 



2. Branches of communication with the superior cervical ganglion of 

 the sympathetic. 



3. A Branch to the Carotid Plexus. 



4. A Pharyngeal branch, which is given off at or near the point where 

 the nerve crosses the external carotid. It is as large as the glossal 

 continuation of the trunk, and it passes on to the wall of the pharynx, 

 behind the stylo-pharyngeus muscle. 



5. A Branch to the Stylo-pliaryngeus muscle. — This may be detached 

 either before or after the preceding branch. It enters the outer side of 

 the muscle. 



The 12th Cranial Nerve, called also the Hypoglossal (Plate 

 32), leaves the cranium by the condyloid foramen. It passes through 

 the angle of separation of the 10th and 11th nerves, and descends on 

 the guttural pouch, crossing to the outer side of the external carotid at 

 or near the origin of the submaxillary artery. It next crosses the 

 phaiynx in company with the submaxillary artery, and passes under the 

 angle formed by that vessel and its lingual branch. It is continued to 



