THE INTERNAL CAROTID ARTERY. 627 



>ortion in the neck and the temporal bone remain to be dissected. 

 The terminal branches of the carotid are examined with the brain. 



Dissection (fig. 225, p. 628). For the display of the cervical Dissection 

 >art of the artery there is now but little dissection required. By the nec k ; 

 letaching the styloid process at the root, and throwing it forward 

 vith its muscles, the internal carotid artery and the jugular vein may 

 be followed upwards to the skull. Only a dense fascia conceals them ; 

 mcl this is to be taken away carefully, so that the branches of the 

 nerves may not be injured. 



In the fascia, and directed forwards over the artery, seek the 

 glosso-pharyngeal nerve, and its branches near the skull, and the 

 mall pharyngeal branch of the vagus lower down ; still lower, the 

 superior laryngeal branch of the vagus, with its external laryngeal 

 >ttset, crossing beneath the carotid. Between the vein and artery, 

 :lose to the skull, will be found the vagus, hypoglossal, and 

 ympathetic nerves : and crossing backwards, over or under the and of the 

 'eiu, the spinal accessory nerve. External to the vessels the loop of ner ves ; 

 he first and second cervical nerves over the transverse process of the 

 atlas is to be defined ; and from it branches of communication are 

 to be traced to the large ganglion of the sympathetic beneath the 

 artery, and to the vagus and hypoglossal nerves. The dissection of 

 these nerves from the carotid vessels at the base of the skull is a 

 difficult operation in consequence of the strong investing tissue. 

 Ascending to the cranium, on the inner side of the carotid, the 

 tscending pharyngeal artery will be met with. 



The INTERNAL CAROTID ARTERY (fig. 225, d) Springs from the internal 



bifurcation of the common carotid trunk. It extends from the upper carotid, 

 border of the thyroid cartilage to the base of the skull ; then through enters the 

 the petrous portion of the temporal bone ; and lastly along the base s " ' 

 of the skull to the anterior clinoid process, where it ends in branches 

 for the brain. This winding course of the artery may be divided its course 

 into three portions one in the neck, another in the temporal bone, 1S 

 and a third in the cranium. 



C'-rncul part. In the neck the artery ascends almost vertically through 

 from its origin to the carotid canal, and is in contact with the the neck ' 

 pharynx on the inner side. The line of the common carotid artery 

 would mark its position in the neck. Its depth from the surface 

 varies like that of the external carotid ; and the digastric muscle 

 may be taken as the index in this difference. Thus, below that less deep 

 muscle, the internal carotid is overlapped by the stern o-mastoid and ow ' 

 covered by the common integuments, fascia, and platysma, and is on 

 the same level as the external carotid, though farther back. But 

 above that muscle, the vessel is placed deeply beneath the external but very 

 carotid artery and the parotid gland, and is crossed by the styloid deep above 

 process and the stylo- pharyugeus muscle. While in the neck, the 

 internal carotid lies on the rectus capitis anticus major muscle, which rests on 

 separates it from the vertebrse. 



Vein. The internal jugular vein accompanies the artery, being position of 

 contained in a sheath with it and placed on its outer side. vein > 



s s 2 



