88 



LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



traverse them, just as do the fibres from the nucleus caudatus 

 and the putamen, and again, like the latter, they are gathered up 

 into a thick bundle below the nucleus lentiformis, in which situ- 

 ation they are called the ansa lenticularis. Most of the fibres 

 of the ansa lenticularis. after passing through the capsule, extend 

 to the region below the thalamus, called the regio subthalamica. 

 The accompanying cut represents a section through the brain 

 of an eight months' foetus, and shows the relations of the teg- 



FIG. 51. 



Frontal section through the brain of a fnetus of abont 32 weeks. All the medullary 

 Ibres stained black by haematoxylin. The tegrnental radiat'on (above), cvusa lenticu- 

 avis (below), and anterior commissure (below and externally) are medullary. There 



are as yet no medullary fibres in the putamen or nucleus caudatus. 



mental tract to the nucleus lentiformis. At this period of devel- 

 opment there are, witli the exception of those shown in Fig. 51, 

 no medullary fibres in the brain. The fibres which arise in the 

 putamen and the nucleus caudatus have not yet appeared. It 

 was only possible to gain an insight into the relations between 

 the nucleus lentiformis and the tegmental radiation by studying 

 the fetal brain. 



In this figure the bundle which passes directly from the 



