THE SIXUSES OF THE DURA MATER. 657 



of the temporo-sphenoidal lobe, and, running along the fissure of Sylvius, opens 

 in: > ihe cavernous sinus. Another large vein, the great anastomotic vein of Tro- 

 1'ird, commences on the parietal lobe, runs along the horizontal limb of the fissure 

 of Sylvius and opens into theanterior 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 

 chor . 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 firm one before opening into the straight sinus. 



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

 and thalaimis 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 

 vena; 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 forward and inward 

 across the superior vermiform process, and terminate in the straight sinus ; some 

 open into the venae Galeni. The inferior cerebellar reins, of large size, run trans- 

 versely outward, and terminate by two or three trunks in the lateral sinuses. The 

 lateral cerebellar veins terminate in the superior petrosal sinuses. 



The perivasc-ular lymph-sheaths alluded to above (see page 87) are especially found in con- 

 nection 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 fifteen in number, and are divided into 

 tw.. 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. Straight Sinus. 



Inferior Longitudinal. Lateral Sinuses. 



Occipital Sinus. 



The Superior Longitudinal Sinus occupies the attached margin of the falx 

 cerebri. Commencing at the foramen ca?cum. through which it constantly com- 

 municates by a small branch with the veins of the nasal fossie. it runs from before 

 backward, grooving the inner surface of the frontal, the adjacent margins of the 

 two parietal, and the superior division of the crucial ridge of the occipital bone, 

 and terminates by opening into the torcular Herophili. The sinus is triangular 

 in form, narrow in front, and gradually increasing in size as it passes backward. 

 On examining its inner surface it presents the internal openings of the superior 

 cerebral veins, which run. for the most part, from behind forward, and open chiefly 

 at the back part of the sinus, their orifices being concealed by fibrous folds; 

 numerous fibrous bands (chordae Willisii) are also seen, extending transversely 

 across the inferior angle of the sinus : and. lastly, some small, white, projecting 

 bodies, the glundulie Pacchioni. This sinus receives the superior cerebral veins, 

 numerous veins from the diploe and dura mater, and, at the posterior extremity 



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