BASAL GANGLIA OF THE CEEEBEAL HEMISPHEEE. 



637 



(viz., from 

 the lateral 



Digitationes 

 hippocampi 



Hippocampus 



Collateral 

 eminence 



Trigonum 

 collaterale 



Posterior horn of 

 lateral ventricle 



Calcar avis 

 Bulb of the cornu 



stood that the arcuate chorioid fissure, throughout its whole length 

 the interveutricular foramen to the extremity of the inferior horn of 

 ventricle), is formed by the 

 involution of the roof and a 

 portion of the wall of the 

 hemisphere which remains 

 epithelial. In the central 

 part of the ventricle this layer 

 is attached, on the one hand, 

 to the sharp margin of the 

 fornix, and on the other to 

 the superior surface of the 

 thalamus ; in the inferior horn 

 it is attached, in like manner, 

 to the edge of the fimbria hip- 

 pocampi or crus of the fornix, 

 whilst, above, it joins the roof 

 of this portion of the ventricle 

 along the line of the stria 

 terminalis (Fig. 564). 



The eminentia collateralis 

 shows very great differences 

 in its degree of development. 



The trigonum collaterale is 

 a smooth elevation in the floor 

 of the ventricle, in the interval 

 which is left between the 

 calcar avis and the hippo- 

 campus as they diverge one 

 from the other. 



BASAL GANGLIA OF THE 



CEREBRAL HEMISPHERE. FlG 555. DISSECTION from above, to show the posterior and 



, , . inferior cornua of the lateral ventricle, 



heading are B . G . Cauda fascia; dentat{e> F .D. Fascia dentata hippocampi. 



3luded Certain masses Ot F . Fimbria hippocampi. H.C. Gyrus hippocampi. 



gray matter more or less com- 

 pletely embedded in the white medullary substance of the hemisphere, and which 

 are developed in its wall. They compose the caudate and lentiform nuclei, which 

 together form the corpus striatum, and the amygdaloid nucleus. 



The nucleus caudatus bulges into the lateral ventricle. It is a piriform, 

 highly arched mass of gray matter, which presents a thick, swollen head, or anterior 

 extremity, and a long, attenuated tail. The head projects into the anterior horn of 

 the lateral ventricle, whilst its narrower part is prolonged laterally and posteriorly 

 in the floor of the ventricle, where it is separated from the thalamus by the stria 

 terminalis. Finally, its tail curves downwards with a bold sweep and enters the 

 inferior horn of the lateral ventricle. In the roof of this horn it is prolonged 

 forwards to the amygdaloid nucleus, the lower part of which it joins. The caudate 

 nucleus thus presents a free ventricular surface, covered with ependyma, and a deep 

 surface embedded in the white substance of the cerebral hemisphere, and for the 

 most part related to the internal capsule. 



Owing to its arched form it follows that, in' horizontal sections through the 

 cerebral hemisphere below a particular level, it is cut at two points, and both the 

 head and the tail appear on the field of the section (Fig. 567). In frontal sections 

 behind the amygdaloid nucleus, it is also divided at two places. 



The anterior extremity of the head of the caudate nucleus coincides very nearly 

 with that of the anterior horn of the lateral ventricle. In the region of the sub- 

 stantia perforata anterior, the head of th'e caudate nucleus gains the surface and its 

 gray matter becomes continuous with that of the cerebral cortex. 



