1 62 ELEMENTS OF HISTOLOGY. [Chap. xvm. 



215. The ttialamus opticus consists of a super- 

 ficial layer of white, and a centre of grey matter. 

 In this numerous multipolar ganglion cells are noticed. 

 The white matter in the outer portion is very con- 

 siderable, and of great importance from its connec- 

 tions. From it radiate tracts of medullated nerve- 

 tibres, which join the tracts of the internal capsule on 

 their way to and from the diiferent parts of the 

 cerebral hemisphere. 



The superior peduncle of the cerebellum, after its 

 decussation with that of the opposite side, passes 

 into the white matter of the thalamus. The trac- 

 tus opticus is connected with the outer white matter 

 of the posterior portion of the thalamus i.e. t the 

 pulvinar. 



216. The corpus striatum, as stated before, 

 is considered as the ganglion of the cerebral hemi- 

 sphere. It consists of the nucleus caudatus and the 

 mwleus lenticular is. The former projects into the 

 lateral ventricle, the latter is the outer portion of 

 the corpus striatum. The nucleus lenticularis is 

 separated from the nucleus caudatus and from the 

 anterior portion of the thalamus opticus by tracts of 

 medullated nerve-fibres, known as the internal capsule. 

 On the outer surface of the nucleus lenticularis is a 

 thin lamina of white matter which is the external 

 capsule. This is separated from the white matter 

 of the cerebral convolutions at this part i.e., the 

 island of Reil by a thin lamina of grey matter, called 

 the claustrum. The nucleus caudatus and lenti- 

 cularis. consist of grey matter with larger and smaller 

 groups of multipolar ganglion cells, permeated by 

 tracts of medullated nerve-fibres, which originate in 

 the grey matter. These tracts of white matter pass 

 transversely and obliquely into the internal capsule, 

 and are to be traced on the one hand to the white 

 matter of the convolutions of the cerebral hemisphere, 



