348 DISSECTION OF THE EABBIT 



iii. The hippocampus major is a prominent convex 

 ridge, projecting into the floor and inner side 

 of the descending cornu, along its whole 

 length. 



iv. The corpus striatum is a thickened part of the 

 wall of the hemisphere, forming the outer side 

 and floor of the anterior part of the lateral 

 ventricle. It lies in front of the hippocampus 

 major, from which it is separated by a deep 

 groove, running obliquely backwards and out- 

 wards across the floor of the ventricle. 



Gut away carefully the outer wall of the anterior cornu of 

 the lateral ventricle, including the corpus striatum. 



v. The ■ septum lucidum is the thin vertical inner 

 wall of the hinder part of the anterior cornu. 

 It is plaiced opposite the corpus striatum, and 

 ventral to the corpus callosum. 



vi. The foramen of Monro is a small hole imme- 

 diately beneath the hinder border of the septum 

 lucidum, through which the lateral ventricle 

 communicates with the third ventricle, or 

 cavity of the thalamencephalon. 



vii. The posterior pillar of the fornix is a narrow 

 band, lying along the anterior edge of the 

 hippocampus major. Posteriorly it follows 

 the hippocampus into the descending cornu ; 

 while anteriorly it becomes continuous with 

 its fellow of the opposite side in the median 

 plane, forming the body of the fornix, imme- 

 diately above the foramen of Monro. 



viii. The choroid plexus is a thin vascular fold of 

 the inner wall of the hemisphere, projecting 

 into the descending cornu in front of the 

 hiJ)pocampus major, and closely appHed to the 

 anterior surface of the latter along its whole 

 length. 



ix. The ' fifth ventricle ' is a median vertical cleft 



