4 
BASAL GANGLIA OF THE CEREBRAL HEMISPHERE. 537 
always a very strongly-marked elevation, which corresponds with the mid-collateral 
fissure, but in the course of growth it is apt to lose much of its prominence 
The anterior collateral eminence is only occasionally present. It appears ag an 
elongated elevation of varying 
length and prominence, on the 
floor of the descending horn of 
the lateral ventricle, on the 
outer side of the hippocampus 
major. It is formed by the 
anterior portion of the fcetal 
collateral suleus,: when this 
develops as a complete fissure. 
—Pes hippocampi 
BASAL GANGLIA OF THE 
CEREBRAL HEMISPHERE. 
Hippocampus 
major 
Anterior 
~ collateral 
eminence 
Under this heading are 
included certain masses of 
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 len- 
ticular nuclei, which together 
form the corpus striatum, the 
claustrum, and the amygdaloid 
nucleus. 
Thecaudatenucleus bulges 
into the lateral ventricle. It 
is a pyriform, highly-arched 
mass of gray matter, which 
presents a thick, swollen head, 
or anterior extremity, and a 
long, attenuated tail. The Fic, 399.—DiIsseEction, to show the posterior and descending 
head projects into the anterior cornua of the lateral ventricle. 
horn of the lateral ventricle B.G. Giacomini’s band. F.D. Gyrus dentatus. ; 
: F ; 2 F.  Fimbria. H.C. Hippocampal convolution. 
whilst its narrower part is pro- 
longed outwards and backwards in the floor of the body of the ventricle, where it 
is separated from the optic thalamus by the tenia semicireularis. Finally, its 
tail curves downwards with a bold sweep and enters the descending horn of the 
lateral ventricle. In the roof of this 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. 400). In coronal sections 
behind the amygdaloid nucleus, it is also divided at two places (Fig. 375, p. 505). 
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 locus 
perforatus anticus, the head of the caudate nucleus gains the surface and its eray 
matter becomes continuous with that of the cerebral cortex. 
The lenticular nucleus lies on the outer side of the caudate nucleus and optic 
thalamus, and is for the most part embedded within the white medullary substance 
of the cerebral hemisphere. It does not extend either so far forwards or so far 
backwards as the caudate nucleus. Indeed, it presents a very close correspondence 
in point of extent with the insula or island of Reil on the surface. When seen in 
Trigonum 
ventriculi 
Posterior horn of 
lateral ventricle 
—~Calear avis 
~ —~——Bulbofthecornu 
3 
