THE CAUDATE NUCLEUS 877 



inferiorJy into the medial part of the temporal lobe nearly parallel with the supe- 

 rior temporal sulcus. Above, it follows the curved crura (posterior pillars) of the 

 fornix and fimbria; below, it does not extend to the temporal pole by from 2 to 3 

 cm. The roof and lateral wall are, for the most part, like those of the posterior 

 horn, being formed by the tapetum, but medialward a strip of the roof is formed by 

 the attenuated, inferior prolongation, or tail, of the caudate nucleus, together 

 with the inferior extension of the stria terminalis of the thalamus. At the end of 

 the inferior horn the roof shows a bulging, the amygdaloid tubercle, situated at 

 the termination of the tail of the caudate nucleus. This bulging is produced by 

 the amijgdaloid nucleus, an accumulation of grey substance continuous with 

 that of tire cortex of the hippocampal gyrus, and which gives origin to part of the 

 longitudinal fibres coursing in the stria terminalis of the thalamus. 



In the medial wall and floor of the inferior horn the following structures are 

 shown: — (1) In the posterior or trigonal part of the floor is the longitudinal 

 collateral eminence, a bulging, very variable in development in different speci- 

 mens, produced by the collateral fissure. This is often pronouncedly in two parts, 

 a posterior prominence corresponding to the middle portion of the collateral fissure 

 and an anterior prominence (less frequent) produced by the anterior part of the 



Fig. 690. — Dissection of Right Temporal Lobe showing the Medial Wall of the End 

 OF the Inferior Horn of the Lateral Ventricle. (From Spalteholz.) 



y 

 Digitations of ^ 

 hippocampus \^ 



Uncus- 



Fimbria of^ ^ 

 hippocampus^ ~—^ 



Hippocampal fissure 

 Dentate gyrus or fascia 



Substantia reticularis ,<sf'-\ 

 alba (Arnoldi) 



■ Hippocampus 



Collateral eminence 



Hippocampal gyrus'' ^^^^^^^1^^^^ - I 



Taenia fimbriae } 



Collateral fissure 



fissure. (2) Medial to this eminence lies the inferior extension of the chorioid 

 plexus, usualty more voluminous than the part in the body of the ventricle. (3) 

 Partly covered by the chorioid plexus is the hippocampus major, a prominent, 

 sickle-like ridge corresponding to the indentation of the hippocampal fissure. It 

 begins as a narrow ridge posteriorly, at the end of the body of the ventricle, as the 

 extension of the posterior pillar of the fornix, and expands anteriorly as the ven- 

 tricular surface of the uncus. Its surface is not regular, but shows a concave 

 medial margin as distinguished from a wider, convex, lateral surface. Its ter- 

 mination in front {pes hippocampi) is divided by two or three flat, radial grooves 

 into a corresponding number of short elevations known as the hippocampal dig- 

 itations. It is covered by a thick stratum of white substance, the ait'e?<s, arising 

 from its depths and continued mesiaily into the fimbria. (4) The fimbria is so 

 folded that its margin, txBnia fimbrice, lies in the cavity of the inferior horn attached 

 to the chorioid plexus and the thin, non-nervous floor of the chorioid fissure. 



The caudate nucleus (fig. 691).— As reahsed in the study of the lateral ven- 

 tricle, the caudate nucleus is a comma-shaped mass of grey substance with a 

 long, much-curved, and attenuated tail. Its head forms the bulging lateral wall 

 of the anterior horn; thence it proceeds posteriorly in the lateral wall of the body 

 of the ventricle and, at the collateral trigone, curves downward and its tail becomes 



