420 AXGIOLOGY. 



Tlie Prevertebral artery comes off as it crosses the internal 

 carotid, and divides into muscular and meningeal branches, the 

 muscular going to the anterior straight muscles of the head and 

 occipito-atloidean articulation. The meningeal are small superior 

 and inferior branches, which are distributed to the dura mater 

 through the foramen lacerum basis cranii.and the condyloid foramen. 



The Mastoid artery leaves the trunk opposite the pre- 

 vertebral, is directed to the mastoid foramen of the temporal 

 bone, jjassing over the styloid process of the occipital, under the 

 obliquus capitis anticus. It gains the parieto-temporal conduit, 

 and inosculates with the meningeal branch of the internal maxillary 

 artery. It supplies the temporal muscle, and the dura mater. 



The Ramus Anastomotic us* is detached at the under surface 

 of the wing of the atlas ; it passes backwards through the posterior 

 foramen under the obliquus capitis posticus, and inosculates 

 with the vertebral artery. It supplies numerous muscular twigs, 

 and furnishes a direct communication between the carotid and 

 vertebral arteries. 



The Musculo -occipital artery arises from the occipital, in the 

 alar gutter ; covered by the obliquus capitis posticus, it passes 

 transversely outwards to the posterior straight muscles, and 

 divides into ascending muscular and cuticular branches for the 

 occipital region, and descending, which anastomose with the 

 superior cervical artery. 



The Cerebro-spinal artery springs from the occipital in the 

 alar gutter, and enters the neural canal through the internal 

 atloid foramen, traverses the spinal dura mater, dividing on the 

 inferior surface of the cord into an anterior branch, which 

 passes forwards, anastomosing by convergence with its fellow 

 from the opposite side, to form the basilar trunk ; and a 

 posterior branch, which, after a short backward course, likewise 

 anastomoses with its fellow from the opposite side, constituting 

 the middle spinal artery. 



internal carotid artery. 



(Fig. 163. 2.) 



This, the second terminal of the common carotid, is directed 

 upwards towards the base of the skull, to the outer side of the 



* [This artery is described as inconstant and variable ; doubtless it is the 

 latter, but hitherto I do not recollect ever to have sought for it in vain. — Ed.] 



