

CAPSULA INTERNA, COEPUS STHIATUM, INTEHBKAIN-aANGLIA. 257 



embryos, and it is probably the fibers of this bundle which Wernicke and 

 Flechsig have described as arising from the corpus striatum. The latter has 

 also recognized the connection with the thalamus. It has already been 

 described in the chapters on comparative anatomy and there designated as 

 the tractus strio-thalamicus. 



Recently, however, I have succeeded in fully establishing the course of the 

 tracts arising from the corpus striatum in the brain of a dog from which the cortex 

 had been completely removed. In this animal experimented upon, all of the fibers 

 of the corona radiata coming from the cortex were secondarily degenerated and had 

 almost disappeared. It was there recognized with all certainty that very large fiber- 

 masses developed from the head of the nucleus caudatus and from the putamen, 

 which passed toward the base and at the same time somewhat posteriorly in the 

 anterior division of the internal capsule. The greatest part of this fiber-mass turned ^ 

 inwardly at once and was lost in the thalamic ganglia. The part that extended '■ 

 farther downward gradually passed toward the median line to disappear in the gan- ; 

 glia in the region below and behind the thalamus. In the region posterior to the 

 corpora quadrigemina, the entire fiber-system, anteriorly so large, had passed over 

 into the ganglia. Its last tracts were taken up by the substantia nigra. The re- / 

 searches by Mahaim and by Monakow upon the secondary degenerations appearing / 

 after disease in the neighborhood of the corpus striatum show that in man also the/ 

 fiber-system arising there has the relations represented in the diagram opposite. I 



The radiaiio strio-thalamica forms, therefore, a large and important con- 

 necting pathway between the corpus striatum and the ganglia of the interhrain 

 and midbrain. 



The fibers of the tegmental radiation, from the cortex, pass between the 

 divisions of the globus pallidus. They pass through this as white lines, 

 and collect at the base of the lenticular nucleus to form a definite bundle of 

 fibers, which is dorsal to the ansa lentiformis and passes mesially exactly 

 like this. It later extends into the medulla oblongata. 



Most of the fibers of the tegmental radiation pass mesially into the 

 region which lies under the thalamus opticus and is named the regio sub- 

 thalamica. 



The accompanying illustration, a section through the brain of a fetus of 8 

 months, shows the relation of the tegmental fibers to the lenticular nucleus. Ex- 

 cepting the fibers represented, there are no other meduUated fibers present in the 

 entire cerebrum at this embryonic stage. The fibers, in particular, which arise in 

 the nucleus caudatus and the putamen are still entirely wanting. Only after the 

 investigation of the fetal brain was it possible to explain with certainty the relation 

 of the lenticular nucleus and the tegmental radiation to one another. 



In mammals there exists a small fiber-tract which passes laterally along 

 the entire extent of the nucleus caudatus. It begins in front of the head 

 of this ganglion as a few fibers which appear to come out of the head itself. 

 The tract increases more and more in size posteriorly, but becomes smaller 



