THE SINUSES OF THE DURA MATER. 601 



surface of the corresponding hemisphere; they open into the superior cerebral 

 veins, or occasionally into the inferior longitudinal sinus. 



The Inferior Cerebral Veins ramify on the lower part of the outer and on 

 the under surface of the cerebral hemisphere. Some, collecting tributaries from 

 the under surface of the anterior lobes of the brain, terminate in the cavernous 

 sinus. One vein of large size, the middle cerebral vein, commences on the under 

 surface of the temporal lobe, and, running along the fissure of Sylvius, opens 

 into the cavernous sinus. Another large vein, the great anastomotic vein of Tro- 

 lard, commences on the parietal lobe, runs along the horizontal limb of the fissure 

 of Sylvius, and opens into the anterior part of the cavernous sinus under the lesser 

 wing of the sphenoid. Others commence on the under surface of the base of the 

 brain, and unite to form from three to five veins, which open into the superior 

 petrosal and lateral sinuses from before backward. 



The Deep Cerebral, or Ventricular Veins (vence Galeni}, are two in number. 

 They are formed by the union of two veins, the vena corporis striati, and the 

 choroid vein, on either side. They run backward, parallel with one another, 

 between the layers of the velum interpositum, and pass out of the brain at 

 the great transverse fissure, between the posterior extremity, or splenium, of the 

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

 two veins usually unite to form one, the vena magna Graleni, before opening into 

 the straight sinus, just before their union they receive the basilar vein. 



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

 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 Basilar vein commences at the anterior perforated space at the base of the 

 brain by the union of a small anterior cerebral vein, which courses backward 

 between the anterior lobes of the cerebrum, with the deep Sylvian vein, which 

 descends through the lower part of the Sylvian fissure. It passes backward round 

 the crus cerebri, receiving the inferior striate vein from the corpus striatum, inter- 

 peduncular veins from the interpeduncular space, ventricular veins from the middle 

 cornu of the lateral ventricles, and tributaries from the uncinate convolution, and 

 enters the vein of Galen just before its junction with the vein of the opposite side. 



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

 in three sets, superior, inferior, and lateral. The superior pass partly forward 

 and inward, across the superior vermiform process, to terminate in the straight 

 sinus and the venae Galeni, partly outward to the lateral and superior petrosal 

 sinuses. The inferior cerebellar veins, of large size, terminate in the lateral, 

 superior petrosal, and occipital sinuses. 



The perivascular lymphatics alluded to in the section on General Anatomy are especially 

 found in connection with the vessels of the brain. These vessels are enclosed in a sheath, 

 which acts as a lymphatic channel, through which the lymph is carried to the subarachnoid 

 and subdural spaces, from which it is returned into the general circulation. 



The Sinuses of the Dura Mater. 



The sinuses of the dura mater are venous channels, analogous to the veins, their 

 outer coat being formed by the dura mater ; their inner, by a continuation of the 

 lining membrane of the veins. They are fourteen in number, and are divided into 

 two sets : 1, those situated at the upper and back part of the skull ; 2, those at 

 the base of the skull. The former are the 



Superior Longitudinal Sinus. Straight Sinus. 



Inferior Longitudinal Sinus. Lateral Sinuses. 



Occipital Sinus. 



