258 



ANATOMY OF THE CENTRAL NEKTOUS SYSTEM. 



in consequence of the slenderness of the tail of the nucleus, and is to be 

 traced no farther than the nucleus itself. The bundle lies in the angle 

 between the surface of the nucleus caudatus and the roof of the ventricle; 

 the fibers of the corpus callosum radiate directly over it. The fibers of the 

 bundle appear to me to come from the nu.cleus caudatus itself, and to return 

 into it again. It is called the association-hundle of the nucleus caudatus 

 (Sachs); but I cannot sharply separate it from the fronto-occipital associa- 

 tion-bundle, which lies close to it. 



You have now become acquainted with the origin and the proximal 

 part of a large number of the fibers which go to make up the forebrain. 



Fig. 167. — Frontal section through the brain of a, fetus of about thirty- 

 two weeks. All meduUated nerve-fibers stained black by htematoxylin. Teg- 

 mental radiation (above), ansa lentiformis (below), and anterior commissure 

 (below and external) are medullated. No medullated fibers are as yet seen in 

 the putamen and the nucleus caudatus. 



Let us now turn to the regions where the majority of the medullated tracts 

 of the cerebrum terminate. 



Back of the cerebrum lies the interirain. Its lateral walls are the 

 thalami optici. These consist of several gray nuclei, which are not sharply 

 separated from one another. White medullated fibers, the stratum zonale, 

 cover the thalamus. They may be traced, on the one hand, in a direction 

 toward the base of the brain into the optic nerves; on the other hand, they 



