898 



THE NERVOUS SYSTEM 



ventricle. Posteriorly the continuation of this lateral extension appears as an in- 

 vagination into the lateral ventricle through the floor of the chorioid fissure. The 

 blood-vessels of the border projecting into the lateral ventricle are amplified into a 

 plexus which appears as a strip of reddish, tabulated, villus-like processes known as 

 the chorioid plexus of the lateral ventricle. 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 downwards into the 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 te!a chorioidea 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 at the interventricular foramen with the plexus of the 

 lateral ventricle of each side. 



FIG. 669. DIAGRAM OF CORONAL SECTION OF CEREBRUM THROUGH MIDDLE OF THALAMEN- 

 CEPHALON SHOWING RELATIONS OF PlA MATER ENCEPHALI AND CHORIOID PLEXUSES OF 

 THIRD AND LATERAL VENTRICLES. 



FIFTH TEXTRICLE 



LA TKIIAL 

 VEXTJ11CLE 



CA UDA TE 



NUCLEUS 



LAMINA 



AFFIX A 



Vena terminatis 



STRIA TER- 

 I/M ALIS OF 

 TBALA.VCS 



PUTA- 

 MES 



22 



la 



GLO- 

 BUS 

 PALLI- 

 DUS 



CAUDATE 



rtlitnioiD 



PLEXUS 



INFERIOR 



CORNU OF 



LA TERAL 



YEXTRICLE 



FIMBRIA 



DEXTATK 

 FASCIA 



FOOT fIF 

 J.\'l A/i'.V II, 

 CAPSl'LE 



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

 epithelial chorioid lamina, which is but a reflexion of the epithelium lining the cavities 

 throughout. The blood-vessels 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 behind the uncus, and also by the 

 chorioidal branches of the posterior cerebral artery, which 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 3 terminates (veins of the corpus stri- 

 atum) , which, in their turn, go to form the greater part of the veins of Galen. Thence 

 the blood passes by way of the vena cerebri magna into the straight sinus. It is prob- 

 able that a large part of the cerebro-spinal fluid is derived by diffusion through the 

 walls of the vessels of the chorioid plexuses. 



