900 THE VASCULAK SYSTEM. 



septum nasi, which is a branch of the spheno-palatine artery. In its course forwards in 

 the roof of the mouth the great palatine artery supplies the gums and the mucous 

 membrane of the hard palate, and also the palatine and maxillary bones. 



(d) The artery of the pterygoid canal is a long, slender branch, usually given off 

 from the descending palatine ; it runs backwards through the pterygoid canal with the 

 corresponding nerve (Vidian), and supplies branches to the upper part of the pharynx, 

 to the levator and tensor veli palatini muscles, and to the auditory tube. One of the 

 latter branches passes along the wall of the auditory tube to the tympanic cavity, where 

 it anastomoses with the other tympanic arteries. 



(e) The pharyngeal branch is a small artery which runs backwards, with the pharyngeal 

 branch of spheno-palatine ganglion, through the pharyngeal canal 'to the roof of the 

 pharynx. It supplies the upper and posterior part of the roof of the nose, the roof of the 

 pharynx, the sphenoidal sinus, and the lower part of the auditory (Eustachian) tube, and 

 anastomoses with the pterygoid branch of the internal carotid. 



(/) The spheno-palatine branch springs from the termination of the internal maxillary 

 artery. It passes medially, through the spheno-palatine foramen, into the nasal cavity, 

 where it gives off (a) a branch to the sphenoidal sinus, and (b) a branch which may replace 

 the pharyngeal artery and which has a similar course and distribution. Then it divides into 

 lateral and septal posterior nasal branches. The lateral posterior nasal branches supply 

 the lateral wall of the nasal cavity and the sinuses which open through it, and they 

 anastomose with the posterior and anterior ethmoidal arteries and* the lateral nasal 

 branch of the external maxillary. The septal posterior nasal branch accompanies the 

 posterior septal nerve across the roof of the nasal cavity and then anteriorly and down- 

 wards in the groove on the vomer. It anastomoses with the great palatine artery and 

 the septal branch of the superior labial. 



ARTERIA CAROTIS INTERNA. 



The internal carotid artery (Figs. 759, 761, 764, and 788) commences at the 

 termination of the common carotid, opposite the upper i border of the thyreoid 

 cartilage, and terminates in the middle fossa of the skull, close to the commence- 

 ment of the stem of the lateral fissure (Sylvius), where it divides into the middle 

 and anterior cerebral arteries. 



Course. From its origin in the carotid triangle it ascends to the base of the 

 skull, lying first in the carotid triangle, medial to the anterior border of the 

 sterno-mastoid, and then between the areolar tissue behind the lateral border of 

 the pharynx, medially, and the posterior belly of the digastric and the styloid 

 process and its muscles laterally. At its commencement it lies postero-lateral to 

 the external carotid, but as it ascends it gradually passes to the medial side of the 

 external carotid, from which it is separated by the styloid process, the stylo- 

 pharyngeus muscle, the glosso-pharyngeal nerve, and the pharyngeal branch of the 

 vagus. 



At the base of the skull it enters the carotid canal, in which it ascends, anterior 

 to the tympanum and the cochlea ; then it turns antero-medially to the apex of 

 the bone where it enters the foramen lacerum, through which it ascends, along the 

 side of the body of the sphenoid, to the middle fossa of the cranium. 



In the middle fossa it runs forwards, in the lateral wall of the cavernous sinus, 

 bo the small wing of the sphenoid ; there it turns backwards along the medial 

 border of the anterior clinoid process, which it grooves. At the posterioi 

 extremity of the process it turns upwards to its termination at the medial end oi 

 the stem of the lateral fissure (Sylvius), below the medial part of the anterioi 

 perforated substance. 



Relations. The relations of the various parts of the artery require separat* 

 consideration 



In the Neck. Posterior. The longus capitis (O.T. rectus capitis anticus major), th< 

 prevertebral fascia, and the sympathetic trunk separate it from the transverse processes o 

 the cervical vertebrae, and postero-lateral to it are the internal jugular vein and the vagu 

 nerve. The accessory and the glossopharyngeal nerves are also postero-lateral to th< 

 artery for a short distance, in the upper part of the neck, where they intervene betweei 

 it and the internal jugular vein. Medial or deep to the internal carotid is the externa 



