220 HEAD AND NECK 



The Arteries of the Cranial Cavity. (i) The vertebral 

 arteries ; (2) the internal carotid arteries; (3) the meningeal 

 arteries. 



Arteriae Vertebrales. The vertebral arteries pierce the 

 spinal dura mater below the foramen magnum, through which 

 they enter the cranium. As each artery passes through the 

 foramen it lies anterior to the highest dentation of the liga- 

 mentum denticulatum, and it passes between the hypoglossal 

 and first cervical nerves. It was divided when the hind brain 

 was removed, and its cut extremity lies near its point of 

 entrance into the cranial cavity. 



Arteriae Carotides Internae. Each internal carotid artery 

 enters the cranium at the lacerate foramen between the apex 

 of the petrous part of the temporal bone and the body of the 

 sphenoid, where it pierces the outer layer of the dura mater. 

 Then it runs anteriorly in the cavernous sinus to the medial 

 side of the anterior clinoid process, where it turns upwards, 

 pierces the inner layer of the dura mater and the arachnoid, 

 and gives off its ophthalmic branch, which runs anteriorly below 

 the optic nerve to the orbit The artery was cut immediately 

 behind its ophthalmic branch during the early stages of the 

 removal of the brain. 



Meningeal Arteries. These are the nutrient arteries of 

 the dura mater, and of the inner table and diploe of the cranial 

 bones. They are derived from a great number of different 

 sources, but the only one of any size is the middle meningeal 

 branch of the internal maxillary artery. The others are 

 small twigs, and, except in a well - injected subject, will 

 not be easily made out. They are : ( i ) anterior meningeal 

 from the anterior ethmoidal artery ; (2) the accessory meningeal 

 from the internal maxillary artery; (3) some small branches from 

 the ascending pharyngeal, occipital, and vertebral arteries. 



Each middle meningeal artery is a branch of the corre- 

 sponding internal maxillary artery. It enters the cranium 

 through the foramen spinosum of the sphenoid, and divides 

 upon the inner surface of the great wing of that bone into two 

 large terminal branches. Of these, the anterior branch ascends 

 upon the great wing of the sphenoid, and the anterior 

 inferior angle of the parietal bone, grooving both deeply, 

 whilst the posterior branch turns posteriorly upon the 

 squamous portion of the temporal bone. The branches 

 which proceed from these trunks spread out widely and, 



