BASAL GANGLIA 



571 



AWGDAI-] 



A. 



lection of gray and white matter and receives its name from the fact that it 

 presents on cross-section a striated appearance. The larger portion of this 

 body is embedded in the cerebral white matter, while the smaller portion 

 projects into the anterior part of the lateral ventricle. A dissection of this 

 nucleus shows that it is subdivided by a band of white matter into two 

 smaller nuclei, viz. : the caudate nucleus and the lenticular nucleus. 



1. The caudate nucleus is a pyriform body which corresponds with the 



intra-ventricular portion of the corpus striatum. It consists of a head, 

 an arching body and a tail. The head, which is thick and large, projects 

 into the anterior cornu of the ventri- 

 cle; the body arches across the ven- 

 tricle from before backward and 

 from within outward, while the tail 

 is directed downward and forward 

 to become associated with the collec- 

 tion of gray matter situated beneath 

 the lenticular nucleus and known as 

 the amygdaline nucleus. Anteriorly, 

 the caudate nucleus is united with 

 the lenticular nucleus by a narrow 

 bridge of gray matter, partially sub- 

 divided by small bands or strands of 

 nerve-fibers passing through it. 



2. The lenticular nucleus is an irregularly 



triangular pyramidal- shaped body 

 and corresponds with the extra-ven- 

 tricular portion of the corpus stria- 

 tum, the portion embedded in the 

 cerebral white matter. The apical 

 extremity of the nucleus is directed 

 toward the median line while its 

 convex base is directed toward and 

 runs almost parallel with the gray 

 matter of the Island of Reil. The 

 general appearance and relation of 

 these nuclei are shown in Figs. 237 

 and 240. A horizontal section of the lenticular nucleus shows that iris 

 divided by two lamina of white matter into three portions. The two in- 

 ner, from their pale yellow color, form the globus pallidus, the outer, 

 somewhat darker in color, is termed the putamen. External to the len- 

 ticular nucleus is a thin stratum of gray matter, arranged more or less 

 vertically, and placed between the outer surface of the lenticular nucleus 

 and the cortex of the Island of Reil, and known as the. claustrum. 

 The optic thalamus is an oblong mass of gray matter situated between 

 the sensor, afferent pathway and the cortex of the cerebrum. The anterior 

 and posterior extremities of each thalamus present enlargements known 

 respectively as the anterior tubercle and the posterior tubercle or pulvinar. 

 The mesial surface of the thalamus forms the lateral wall of the third ventri- 

 cle and is covered by epithelium resting on a thin layer of ependyma. ' ;;Y, 

 A transection of the thalamus shows that it is not only covered 'externally 



-AMYGDALA 



FIG. 237. Two VIEWS OF A MODEL 

 OF THE STRIATUM. A, Lateral aspect; B, 

 mesial aspect. ( Spitzka.) 



