THE NERVOUS SYSTEM. 



2OI 



The corpus striatum consists of both white and gray 

 matter. The latter, composed of cells, is disposed in 

 two chief nuclei or masses, known as the nucleus cauda- 

 tus, lying median and cephalic, and the nucleus lenticu- 

 laris, which is more lateral and caudal (Fig. 95). The 

 center of the nucleus lenticularis is laterad of the optic 

 thalamus and dorsad of the crus cerebri. A thin layer 

 of white matter, the lamina semicircular is, separates the 



vn cm 



FIG. 95. CROSS-SECTION OF THE BRAIN THROUGH THE ANTERIOR COM- 

 MISSURE. 



an, Arachnoid; ce, external capsule; d, corpus callosum; cm, anterior 

 commissure ; /.re, falx cerebri ; /, great longitudinal fissure ; fx, anterior 

 pillars of the fornix; ic, internal capsule; n, radiating fibers of cal- 

 losum ; in, septum lucidum ; nc, nucleus caudatus of corpus striatum ; 

 /, nucleus lenticularis; p, pia mater; vis, superior longitudinal sinus; 

 vn, third ventricle; v, lateral ventricle. 



optic thalamus from the nucleus caudatus. A few fibers 

 from the crus cerebri form the lamina semicircularis, 

 whose edge may be seen in the floor of the lateral ven- 

 tricle on the lateral boundary of the nucleus caudatus. 

 A group of fibers, known as the internal capsule, separates 

 the optic thalamus from the nucleus lenticularis, laterad 

 of which is the external capsule, a group of fibers probably 

 descending from the cells of the cerebral cortex. The two 

 nuclei of the corpus striatum are connected by fibers, 

 17 



