CEREBRAL. 541 



veins of the pericranium. They are divided into the frontal, which opens into 

 the supraorbital vein, by an aperture at the supraorbital notch; the anterior 

 temporal, which is confined chiefly to the frontal bone, and opens into one of 

 the deep temporal veins, after escaping by an aperture in the great wing of the 

 sphenoid ; the posterior temporal, which is confined to the parietal bone, and 

 terminates in the lateral sinus by an aperture .at the posterior inferior angle of 

 the parietal bone ; and the occipital, which is confined to the occipital bone and 

 opens either into the occipital vein, or the occipital sinus. 



CEREBRAL YEINS. 



The Cerebral Veins are remarkable for the extreme thinness of their coats, 

 in consequence of the muscular tissue in them being wanting, and for the 

 absence of valves. They may be divided into two sets, the superficial, which 

 are placed on the surface, and the deep veins, which occupy the interior of the 

 organ. 



The Superficial Cerebral Veins ramify upon the surface of the brain, being 

 lodged in the sulci, between the convolutions, a few running across the convo- 

 lutions. They receive branches from the substance of the brain, and terminate 

 in the sinuses. They are named, from the position they occupy, superior, in- 

 ferior, internal, arid external. 



The Superior Cerebral Veins, seven or eight in number on each side, pass 

 forwards and inwards towards the great longitudinal fissure, where they receive 

 the internal cerebral veins, which return the blood from the convolutions of 

 the flat surface of the corresponding hemisphere; near their termination, they 

 become invested with a tubular sheath of the arachnoid membrane, and open 

 into the superior longitudinal sinus, in the opposite direction to the course of 

 the blood. 



The Inferior Anterior Cerebral Veins commence on the under surface of the 

 anterior lobes of the brain, and terminate in the cavernous sinuses. 



The Inferior Lateral Cerebral Veins commence on the lateral parts of the 

 hemispheres, and at the base of the brain ; they unite to form from three to 

 five veins, which open into the lateral sinus from before backwards. 



Thefnferior Median Cerebral Veins, which are very large, commence at the 

 fore part of the under surface of the cerebrum, and from the convolutions of 

 the posterior lobe, and terminate in the straight sinus behind the vense Galeni. 



The Deep Cerebral, or Ventricular Veins (venae Galeni), are two in number, 

 one from the right, the other from the left, ventricle. They are each formed 

 by two veins, the vena corporis striati, and the choroid vein. They run back- 

 wards, parallel with one another, inclosed within the velum interpositum, and 

 pass out of the brain at the great transverse fissure, between the under surface of 

 the corpus callosum and the tubercula quadrigemina, to enter the straight sinus. 



The vena corporis striati commences in the groove between the corpus striatum 

 and thalamus opticus, receives numerous veins from both of these parts, and 

 unites behind the anterior pillar of the fornix with the choroid vein, to form 

 one of the venae Galeni. 



The choroid vein runs along the whole length of the outer border of the., 

 choroid plexus, receiving veins from the hippocampus major, the fornix and 

 corpus callosum, and unites at the anterior extremity of the choroid plexus, 

 with the vein of the corpus striatum. 



The Cerebellar Veins occupy the surface of the cerebellum, and are disposed 

 in three sets, superior, inferior, and lateral. The superior pass forwards and 

 inwards, across the superior vermiform process, and terminate in the straight 

 sinus ; some open into the venas Galeni. The inferior cerebellar veins, of large 

 size, run transversely outwards, and terminate by two or three trunks in the 

 lateral sinuses. The lateral anterior cerebellar veins terminate in the superior 

 petrosal sinuses. 



