924 



THE NERVOUS SYSTEM 



low into each lateral ventricle. The blood-vessels of the border proj ecting into the 

 lateral ventricle are amplified into a plexus which appears as a strip of reddish, 

 lobulated, villus-like processes known as the chorioid plexus of the lateral ven- 

 tricle. The plexus, being in the border of the tela, begins at the interventricular 

 foramen, extends through the body or central portion of the ventricle, and down- 

 ward into its inferior cornu. It is most developed at the junction of the body with 

 the inferior cornu, and is there known as the glomus chorioideum. 



From the under surface of the chorioid tela of the third ventricle, hanging 

 down on either side of the mid-line into the cavity of the ventricle, are two other 

 longitudinal, lobulated strands of blood-vessels which are the chorioid plexuses of 

 the third ventricle. At the anterior end of the third ventricle these two plexuses 

 join with each other and also T^dth the plexus of the lateral ventricle of each side 

 through the interventricular foramina. 



The chorioid plexuses of both the ventricles are covered by a layer of ependyma, epithelial 

 chorioid lamina, which is but a reflexion of the ependyma lining the cavities throughout and 

 represents the remains of the germinal layer of the embryonic brain vesicles. The blood-vessels 



Fig. 729. — Diagram of Coronal Section of Cerebrum through Middle of Thalamen- 



CEPHALON SHOWING RELATIONS OF PlA MaTER EnCEPHALI AND ChORIOID PlEXUSES OP 



Third and Lateral Ventricles. 



Fifth ventricle 



Lateral ven- 

 tricle 



Caudate 



nucleus 



Lamina affixa 



Vena ter- 



minalis 



Stria ter- 



minalis of 



thalamus 



f Puta- 



men 



Fornix 



« (fl 



02 



0) w 



Globus 

 pallidus 



Caudate 

 nucleus 

 Chorioid 

 plexus 

 Inferior cornu 

 of lateral 

 ventricle 



Fimbria 



Dentate gyrus 



Mammillo- 

 thalamic 

 fasciculus 



Internal 

 capsule 



of the chorioid plexus of the lateral ventricle receive blood by the chorioid artery (a direct branch 

 of the internal carotid), which enters the plexus through the chorioid fissure immediately mesial 

 to the uncus, and also by the chorioidal branches of the posterior cerebral artery, wliich supply 

 the plexus of the body of the ventricle. The chorioid plexuses of the third ventricle receive blood 

 chiefly by branches from the superior cerebellar arteries. The greater part of the blood of both 

 plexuses passes out by way of the tortuous chorioid veins, which, at the interventricular foramen, 

 empty into the vena; terminales (veins of the corpus striatum), which, in their turn, go to form 

 the greater part of tlie veins of Galen. Thence the blood passes by way of the vena cerebri 

 magna into the straight sinus. It is probal)le that a large part of the cerebro-spinal fluid of the 

 third and lateral ventricles is derived by difTusion through the walls of the vessels of the chorioid 

 plexuses. 



THE rKJiJPllKliAL NP:RV0US SYSTEM 



The intimate connection and consequent control exercised by the central 

 nervous system over all the tissues and organs of the body is attained through the 



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