436 THE BRAIN 



On the floor of the inferior horn the dissector will note 

 the following parts." (i) the hippocampus; (2) the chorioid 

 plexus; (3) the fimbria ; and (4) the eminentia collateralis. 



Hippocampus (O.T. Hippocampus Major). The hippo- 

 campus is overlapped by the chorioid plexus, which must be 

 turned aside. It is a prominent elevation in the floor of the 

 inferior horn of the lateral ventricle, and is strongly curved 

 in conformity with the course taken by the horn in which it 

 lies. It presents, therefore, a concave medial margin and a 

 convex lateral margin. Narrow posteriorly, it enlarges as it 

 is traced forwards, and it ends, below the amygdaloid tubercle, 



Optic tract 



Stria terminalis | Fimbria 

 Chorioid plexus | ! / Subthalamic body 

 Caudate nucleus I j ! j ! Basis pedunculi 



Inferior cornu of lateral ventricle ; ! ! ! Red nucleus 



- Collateral eminence Pia mater (red) 



Collateral fissure Cerebellum 



FIG. 170. Frontal Section to show relations of Inferior Cornu of 

 Lateral Ventricle. (Part of Fig. 188 enlarged.) 



in a thickened extremity, the pes hippocampi. The surface 

 of the pes hippocampi is marked by some faint grooves which 

 intervene between a number of ridges called the hippocampal 

 digitations. The hippocampal elevation is due to masses of 

 nerve cells and the nerve fibres associated with them. 



Alveus. The alveus is a thin white layer formed by nerve 

 fibres which arise from the cells of the hippocampus, and 

 spread out over its ventricular surface. 



Fimbria (Hippocampi). The fimbria is a narrow but very 

 distinct band of white matter which is attached by its lateral 

 margin along the concave medial border of the hippocampus, 

 immediately above the fascia dentata. The white matter com- 



