Internal Carotid Artery 33 



and others which enter the bone for the molar and bicuspid teeth, and 

 for the antrum. The infra-orbital passes beneath the floor of the 

 orbit, and emerges from the foramen, beneath the levator labii supe- 

 rioris, to supply the tissues in the neighbourhood and to anastomose 

 with the facial. Whilst in the canal it sends branches up into the orbit, 

 and others down the anterior wall of the antrum the anterior 

 dental for the front teeth. The posterior or descending- palatine 

 branch leaves the spheno-maxillary fossa by a special osseous canal, 

 and turns forwards on to the under surface of the hard palate through 

 the posterior palatine foramen, which is on the inner side' of the last 

 molar tooth. It supplies the hard and soft palate and the tonsil. 



A wound of this vessel may cause serious trouble in the operation 

 for cleft palate, and if pressure fail to stop the bleeding the canal 

 must be plugged by a sharp spigot of wood. The Vidian and the 

 pterygo-palatine branches run back to the pharynx and the Eustachian 

 tube ; the former may also send a twig into the tympanum. The nasal 

 or spheno-palatine branch enters the superior meatus, giving an off- 

 shoot to the septum of the nose, and twigs to the turbinated bones. 



There is no venous trunk corresponding to the external carotid. 



The internal carotid artery runs straight up from its origin at 

 the level of the upper border of the thyroid cartilage to the base of the 

 skull, which it traverses by the tortuous canal in the petrous bone. 

 It then turns forwards in the cavernous sinus, in the groove upon the 

 side of the body of the sphenoid, and upwards on the inner aspect of 

 the anterior clinoid process. Then, having pierced the dura mater 

 near the inner end of the Sylvian fissure, it divides into the anterior 

 and middle cerebral arteries. 



Relations of the internal carotid in the neck. Superficially 

 are the skin, platysma, and fasciae, the anterior border of the sterno- 

 mastoid, the posterior belly of the digastric and the stylo-hyoid, 

 with the hypo-glossal nerve and the occipital artery, and the lingual 

 and facial tributaries of the internal jugular vein ; the external 

 carotid and the stylo-glossus, stylo-pharyngeus, and the glosso- 

 pharyngeal nerve, and, as the artery approaches the petrous bone, 

 the parotid gland. 



The artery rests upon the transverse processes of three upper 

 cervical vertebras and the rectus capitis anticus major ; the superior 

 laryngeal branch of the vagus ; and the superior cervical ganglion of 

 the sympathetic. 



To its inner side are the pharynx and tonsil, and the ascending 

 pharyngeal artery. I have known of a case in which the stem of a 

 clay pipe, driven through the tonsil and the pharynx, caused a fatal 

 laceration of the internal carotid, and I have heard of another in which 

 an aneurysm of the artery, which pushed the tonsil inwards, was in- 

 cised under the belief that the swelling was a tonsillar abscess. 



To its outer side are the internal jugular vein and the vagus. 



D 



