THE CORTEX OF THE FORE-BRAIN, ETC. 79 



lenticular nucleus, and, lastly, fibres from the nucleus caudatus 

 to the inner divisions of the lenticular nucleus, all go to make 

 up the internal capsule, the white mass of fibres shown in the 

 horizontal section. 



Fig\ 46 is intended to complete the picture of those parts 

 given in the horizontal section. It strikes the ganglia of thr 

 corpus striatum far forward, and clearly shows the manner of 

 their separation by the interposed fibres of the internal cnpsule. 



The form and situation of the nucleus caudatus will now 

 be clear to von, but it will be more difficult to form an idea of 



*t 



the peculiar wedge-shaped figure of the lenticular nucleus. A 

 study of the horizontal and of the vertical sections shown in 

 Fig. 4ft will materially aid you. This ganglion is intimately 

 associated internally with two somewhat lighter, grayish gan- 

 glionic masses, which are closely connected to it by nerve-fibres. 

 "We speak ordinarily of the three divisions of the lenticular 

 nucleus, whereas it is probable that only one the broad, dark, 

 outer portion (the putamcn) is morphologically analogous to 

 the nucleus caudatus. The latter, as above stated, sends its 

 fibres through the anterior branch of the internal capsule to the 

 two inner divisions of the lenticular nucleus, and, perhaps, 

 through them and farther caudad. The fibres of the putamen 

 run an exactly similar course.* 



In all vertebrates, from fishes up to birds, a thick bundle 



.of fibres can be seen, arising in the corpus striatum and ending 



partly in a tbalamic nucleus and partly passing- farther back. 



It can only be found with difficulty in human beings, because 



t. * 



too many bundles from the cortex are united with it. Still, I 

 have recognized this basal fore-brain bundle in early embryos, 

 and it is apparently these fibres which Wernicke and Flechsig 

 have described as springing from the corpus striatum. The 

 latter, indeed, recognized their connection with the thalanms. 



* The fibres arising in the ganglia of the corpus striatnm receive their medullary sheaths 

 at a much later period than the tegmental radiation which passes through the inner divisions 

 of the nucleus lentiformis. Hence, we have succeeded in distinguishing these two sets of fibres, 

 which are closely intermingled in the adult. 



