CEREBRAL VEINS. 48 1 



hyiJOglossal nerve ; 1, the right internal carotid artery as it makes its turn in tlie cavern- 

 ous siniis in tlic groove of the sphenoid bone ; 2, its opthalmic liranch 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 rejiresented on the right side as 

 giving oft' the communicating artery to the internal carotid ; 4, basilar artery ; 5, verte- 

 bral arteries giving oft" the anterior spinal ; x , great meningeal vessels spreading upwards 

 from the foramen spinosum ; 6, superior petrosal sinus ; 7, inferior jjetrosal running 

 back into tlie 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 suj^erior longitudinal sinus. 



The superficial veins upon the upper surface of the hemispheres 

 are for the most part lodged in the tortuous sulci between the convo- 

 lutions ; but some run over the convexity of the convolutions. Their 

 general direction is towards the middle line ; and on reaching the 

 margin of the longitudinal fissure between the hemispheres, thev 

 receive branches from the flat mesial surfoce of the hemispheres, and 

 becoming invested by tubular sheaths of arachnoid membrane, incline 

 obliquely forwards and open in that direction into the superior longi- 

 tudinal sinus. 



The veins upon the sides and under surface of the brain are directed 

 outwards, to open into the lateral and other sinuses at each side. 



The deep veins of the brain commence by branches within the 

 ventricles of that organ. Thus, upon the surface of the corpus 

 striatum several small venous branches are seen, which for the most 

 part converge to form a slender vein which runs along the groove 

 between the corpus striatum and optic thalamus, and opens into one 

 of the veins of the choroid plexus. The minute veins of the choroid 

 2^1('xus pass backwards, and incline towards the middle line from each 

 side, so as to form, by their union, two veins — venco Galcni. These, 

 lying parallel, run directly backwards, enclosed within the velum inter- 

 positum, and escape from the interior by passing through the great 

 transverse fissure of the brain between the under surface of the corpus 

 callosum and tlie corpora quadrigemina. In this way they reach 

 the anterior margin of the tentorium cerebelli, at its place of union 

 with the falx cerebri, where they terminate by entering the straight 

 sinus. 



The veins of the ccrelcllmn are disposed in two sets. Those of the 

 upper surface incline inwards and forwards for the most part, and I'un 

 upon the upper vermiform process, over which they ascend a little to 

 reach the straight sinus, in which they terminate ; some, farther for- 

 ward, open into the veins of Galen. Those at the under surface ran 

 transversely outwards, and pour their contents into the occipital and 

 the lateral sinuses. 



CEANIAL SINUSES. 



The venous sinuses within the cranial cavity admit of being' 

 divided into two sets, viz., those placed in the prominent folds of the 

 dura mater, and those situated in the base of the skull. 



The form and size of the sinuses are various. A\\ of them are lined 

 by a continuation of the internal membrane of the veins, the dura 

 mater serving as a substitute for the other coats. 



The sinuses which are contained in the several processes or folds of 



VOL. I. II 



