138 PRACTICAL ANATOMY. 



the veins of Galen. (Fig. 82.) The blood from the cortical system is returned 

 by various veins to the several dural sinuses. 



6. \Vliat becomes of the blood in tlie sinuses f 



The sinuses converge to form the internal jugular vein. This vein is made 

 up at the jugular foramen, and leaves it in company with the ninth, tenth, and 

 eleventh cranial nerves. 



7. Do the branches given off from the ganglionic system communicate with one 

 another or with branches of the cortical system / 



No. 



8. Where do the branches forming the ganglionic system take tlieir origin, and 

 hoiv are they named? 



They originate from the circle of Willis and from its primary branches for an 

 inch beyond the circle. They are named : 



Antero-median, from the anterior communicating artery. 

 Antero-lateral, from the middle cerebral artery. 

 Postero-rnedian, from the posterior cerebral artery. 

 Postero-lateral, from the posterior cerebral artery. 



9. What is the most importer/it function of this system of circulation .' 



To supply blood to the basal ganglia, the most important part of the 

 brain. 



10. Name the most important branch of the ganglionic system, and give its 

 surgical importance. 



The lenticulo-striate artery. It is the largest, and most frequently the seat 

 of embolism or hemorrhage. It passes through the internal capsule. 



1 1 . Do all the brandies of tlie ganglionic system supply basal ganglia / 



No ; the anterior and posterior choroid branches supply the choroid plexuses 

 of the lateral ventricles and some minor adjacent parts. 



12. Has any part of the ganglionic system any tiling to do with the formation 

 of the pia mater f 



As mentioned in a previous paragraph, the anterior and posterior choroid 

 arteries are branches of the ganglionic system, but they do not supply basal 

 ganglia ; they supply the choroid plexuses, in the lateral ventricles, and these 

 plexuses, with the velum interpositum, are extensions from the general pia 

 mater on the surface of the brain to equally superficial parts of the brain, 

 apparently, but not really, on the interior of the brain. 



13. Are the terms pia mater and cortical system of ch dilation, for practical 

 purposes, synonymous ? 



Yes ; the pia mater consists of vessels, arteries and veins, and connective 

 tissue ; the arteries, for the most part, originate beyond the confines of the gang- 

 lionic system. The pia mater is applied to every part of the outer surface of the 

 brain ; it reaches into the fissures and sulci. It forms the velum interpositum 

 and the choroid plexuses. 



1 4. How are the cerebral veins classified ? 



They may be grouped as ganglionic, basilar, and cortical, (i) The central 

 or ganglionic veins come together to form the veins of Galen, having gathered 

 in their course the veins of the choroid plexuses and velum interpositum. 

 The veins of Galen, from the two hemispheres, unite to form the common vein 

 of Galen, a trunk about one-half of an inch in length ; this, as seen previously, 

 opens into the straight sinus. (2) The basilar veins collect the blood from the 

 under surface of the cerebrum, and feed the petrosal, cavernous, and lateral 

 sinuses. (3) The cortical veins gather the blood from the outer and inner 

 surfaces of the hemispheres and feed the superior and inferior longitudinal 

 sinuses in the attached and free margins of the falx cerebri respectively. 



