328 NEUROLOGY, OR ANATOMY OF NERVOUS SYSTEM 



The velum interpositum is a process of the pia mater which 

 occupies the great transverse fissure, and hence separates 

 the fornix from the third ventricle. In front it sends a process 

 through the foramen of Monro to each lateral ventricle. From 

 its under surface it supplies the two vascular processes which 

 form the choroid plexuses of the third ventricle, and on each 

 side the choroid plexuses of the lateral ventricles are found. 



The Third Ventricle 



This is the expanded interval into which the Sylvian aqueduct 

 opens, and which lies between the optic thalami. The re! inn 

 interpositum, with the choroid plexuses, connected on ich 

 side with the peduncles of the pineal gland, forms its roof to- 

 gether with the posterior commissure. Its floor presents the 

 lamina cinerea, tuber cinereum, infundibulum, corpora albi- 

 cantia, posterior perforated space, and tegmentum of crura. 

 In front it is bounded by the anterior commissure and the 

 lamina cinerea. Behind is the opening of the aqueduct of 

 Sylvius. 



The corpus striatum is a mass of gray matter, and consists 

 of an extra ventricular portion embedded in the hemisphere, 

 and called the lenticular nucleus, and an intraventricular 

 part in the body and anterior cornu, the nucleus caudatus. 



The caudate nucleus is pyriform, projecting into the body 

 and anterior cornu by its broad end, and by its smaller end 

 into the roof of the middle cornu nearly to its tip. 



The lenticular nucleus is divided into three zones, visible 

 on transverse vertical section. It is separated from the caudate 

 nucleus by the internal capsule, and the external capsule separates 

 it from the claustrum. This nucleus and the caudate are joined 

 together in front, being continuous with the gray matter of 

 the anterior perforated space. 



The claustrum is a gray lamina marked externally by ridges 

 and furrows corresponding to the gyres and sulci of the island 

 of Reil. 



The nucleus amygdalce is a small gray mass projecting into 

 the apex of the middle cornu, and continuous with the cortical 

 part of the apex of the temporal lobe. 



