THE FORE-BRAIN OR PROSENCEPHALON 



833 





inferior cornu. Its lower end is enlarged, and presents two or three rounded eleva- 

 tions or digitations which give it a paw-like appearance, and hence it is named 

 the pes hippocampi. If a transverse section be made through the hippocampus, 

 it will be seen that this eminence is produced by the folding of the wall of the 

 hemisphere to form the hippocampal fissure. The main mass of the hippocampus 

 consists of gray substance, but on its ventricular surface is a thin white layer, 

 the alveus, which is continuous with the fimbria hippocampi. 



The collateral eminence (eminentia collateralis) (Fig. 740) is an elongated 

 swelling lying lateral to and parallel with the hippocampus. It corresponds with 

 the middle part of the collateral fissure, and its size depends on the depth and 

 direction of this fissure. It is continuous behind with a flattened triangular area, 

 the trigonum collaterale, situated between the posterior and inferior cornua. 



The fimbria hippocampi is a continuation of the cms of the fornix, and will be 



iscussed with that body; a description of the choroid plexus will be found on 



age 840. 



FIG. 740. Inferior and posterior cornua, 

 viewed from above. 



Fio. 741. Two views of a model of the striatum: A, 

 lateral aspect; B, mesal aspect. 





(The corpus striatum has received its name from the striped appearance which 

 a, section of its anterior part presents, in consequence of diverging white fibers 

 being mixed with the gray substance which forms its chief mass. A part of the 

 corpus striatum is imbedded in the white substance of the hemisphere, and is 

 herefore external to the ventricle; it is termed the extraventricular portion, or the 

 lentiform nucleus ; the remainder, however, projects into the ventricle, and is named 

 the intraventricular portion, or the caudate nucleus (Fig. 737). 



The caudate nucleus (nucleus caudatus; caudatwn) (Figs. 741, 742) is a pear-shaped, 

 highly arched gray mass; its broad extremity, or head, is directed forward into the 

 anterior cornu of the lateral ventricle, and is continuous with the anterior perforated 

 substance and with the anterior end of the lentiform nucleus; its narrow end, 

 or tail, is directed backward on the lateral side of the thalamus, from which it is 



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