54 ANATOMY OF THE CENTEAL NEBVOUS SYSTEM. 



of the cerebrum is a thickening of the wall, which projects freely into the 

 ventricle: the corpus striatum. From the corpus striatum as from the 

 cerebral cortex nerve-fibers arise. 



Many fibers which have their origin in the cerebrum must pass through 

 the corpus striatum on their way to more distant parts of the central nervous 

 system. The fibers thus passing through the corpus striatum lie in two 

 masses: an outer and an inner one. The outer one is called the nucleus 

 lentiformis and the inner one the nucleus caudatus. The mass of fibers 

 between the two has received the name internal capsule. In the four months' 

 human embryo the division of the corpus striatum is already clear, and the 

 nucleus lentiformis and nucleus caudatus appear as independent gray 

 masses. 



The corpus striatum lies the whole length of the cerebral base. Pos- 





Fig. 24. — Showing median aspect of a hemisphere whose lateral or outer 

 aspect is shown in Kig. 23. Stelle wo Vorderhirn u. Zwischenhirn Zusammen- 

 stossen, Place where cerebrum and Thalamencephalon come together. For further 

 description, see text. 



teriorly it is, indeed, very narrow and it is really only the median part 

 which is always demonstrable. As tail of the caudate nucleus, it is alwa}'s 

 found in cross-sections through the cerebrum. The lateral part, the nucleus 

 lentiformis, is much shorter. The nucleus caudatus projects freely into the 

 ventricle. The same is true, anteriorly, of the nucleus lentiformis. In later 

 embryonic life, however, the narrow cleft between it and the cerebral wall 

 becomes so narrow as to be no longer demonstrable. But the cerebral wall 

 may always, even in adults, be easily separated from the outer wall of the 

 nucleus lentiformis, without the severing of fibers. 



In the adult brain the position of the former cleft may become of great 

 importance. At that place, for example, cerebral hemorrhages take place 

 with especial ease, and the blood, even when it is small in quantity, fills the 

 space between the cerebral wall and the outer side of the nucleus lentiformis. 



