256 



ANATOMY 0]? THE CBNTEAL NERVOUS SYSTEM. 



lentiformis, located laterally, and the nucleus caudatus, which lies dorsally 

 and mesially. The nucleus lentiformis consists of an outer division, the 

 putamen, and two or more inner divisions, the globus pallidus. From the 

 putamen and from the nucleus caudatus arises the fiber-system of the corpus 

 striatum. Moreover, the corpus striatum is traversed by a system of fibers 

 originating in the cortex: the tegmental radiation. 



The fiber-system of the corpus striatum itself connects the same with 

 the ganglia of the interbrain. It passes, in part, in the anterior limb of the 

 internal capsule, in part — so far as it comes from the putamen — ^under the 

 internal capsule at the base of the brain, to the interbrain. Thus the latter 

 portion of fibers must surround the fibers of the internal capsule at the 



Fig. 166. — The fiber-system which arises from the nucleus caudatus and 

 passes to the ganglia of the interbrain and midbrain (Radiatio atrio-thalamica) . 

 The fiber-system of the lenticular nucleus is not represented. It would run from 

 the observer toward the thalamus. 



place where they come to lie free at the base of the brain as the pes pedun- 

 culi. This part is designated as the loop of the lenticular nucleus, or ansa 

 lentiformis. It contains essentially the fibers from the putamen. 



We are here concerned with a very old fiber-system, one very important 

 for the entire mechanism of the brain. For in all vertebrates, from fishes 

 up to mammals, there may be demonstrated a well-defined bundle of fibers, 

 which arises in the corpus striatum and in part terminates in a nucleus of 

 the interbrain, in part passes on farther down. In man it is to be fo^md 

 with difficulty, because so many tracts from the mantle region are associated 

 with it. Yet I have recognized this basal bundle of the forebrain in young 



