THE BRAIN. 417 



because it extends backward in a slender, curved, tail-like prolonga- 

 tion ; and the lenticular nucleus (7), which has a somewhat lens-like 

 figure, and is further divided into three concentric zones. Between 

 the lenticular nucleus and the optic thalamus is a band of white sub- 



FIG. 111. 

 i 



"'*' 

 f , V> 



2 



HORIZONTAL SECTION OF THE HEMISPHERES, AT THE LEVEL OF THE CEREBRAL GANGLIA.!. Great 

 longitudinal Fissure, between frontal lobes; 2. Great longitudinal Fissure, between occipital 

 lobes; 3. Anterior part of Corpus Callosum ; 4. Fissure of Sylvius; 5. Convolutions of the Insula : 

 6. Caudate Nucleus of Corpus Striatum; 7. Lenticular Nucleus of Corpus Striatum; 8. Optic 

 Thalamus; 9. Internal Capsule ; 10. External Capsule; 11. Claustrum. 



stance, the internal capsule (9), consisting of fibrous bundles, the con- 

 tinuations of the crura cerebi, passing obliquely upward and outward 

 from below. The optic thalamus (8), situated on the inner side of 

 the internal capsule is of a lighter and more uniform tint than the 

 corpus striatum, since the nerve fibres which penetrate it from 

 below are dispersed in minute brush-like ramifications through its 

 substance. On the outer aspect of the lenticular nucleus is a second 

 envelope of white substance, known as the external capsule (10), 

 with a thin layer of gray substance, the claustrum., or partition (11), 

 and beyond that the white substance and convolutions of the insula 



2B 



