INTRACRANIAL VEINS. 



461 



into the veins of Galen. Those at the under surface run transversely out 

 wards, and pour their contents into the occipital and the lateral sinuses. 



Fig. 312. 



Fig. 312. INTERNAL VIEW OP THE BASE OF THE SKULL, SHOWING THE SINUSES OP THE 



DURA MATER, &c. ^ 



The sinuses of the dura mater have been opened, a small portion of the i-oof of the 

 orbit has been removed posteriorly on the left side, and the dura mater has been dissected 

 so as to bring into view the arteries at the base of the skull, the venous sinuses and the 

 issue of the cerebral nerves. 



I., the olfactory bulb; II., the optic nerves, that on the left side cut short; III., 

 placed on the pituitary body, indicates the third nerve; IV., the trochlear nerve , V., 

 placed opposite to the middle of the three divisions of the fifth nerve as they pass out of 

 the cranium ; VI., the sixth nerve ; VII., the facial and auditory nerves entering the 

 meatus auditorius internus ; VIIL, placed opposite to the three portions of the eighth pair 

 as they pass into their several foramina of the dura mater ; IX., the hypoglossal nerve 

 as it passes to the anterior coadyloid foramen ; 1, the right internal carotid artery as it 

 makes its turn in the cavernous sinus on the groove of the sphenoid bone ; 2, its ophthal- 

 mic branch proceeding into the orbit, below and to the outside of the optic nerve ; 3, 

 division of the basilar artery into the two posterior cerebral arteries, one of which is 

 represented on the right side as giving off the communicating artery to the internal carotid ; 

 4, basilar artery ; 5, vertebral arteries giving the anterior spinal ; x , great meningeal 

 vessels spreading upwards from the foramen spinosum ; 6, superior petrosal sinus ; 7, 

 inferior petrosal running back into the lower part of the lateral sinus ; 8, termination of 

 the lateral sinus in the internal jugular vein, and continuation of the lateral sinus ; 

 8', commencement of the lateral sinus ; 9, occipital sinuses; 10, torcular Herophili, and 

 below that number in the figure, the superior longitudinal sinus. 



CRANIAL SINUSES. 



The venous sinuses within the cranial cavity admit of being divided into 



