230 A MANUAL OF ANATOMY. 



mens (and in the original photographs) shows the lenticu- 

 lar nucleus to consist of three portions vertically divided 

 by thin striations of white fibres (the external and internal 

 medullary laminae). The two inner portions of the nucleus 

 are lighter in color than the outer portion ; the former con- 

 stitute the globus pallidus, the latter the putamen. 



The Optic Thalami. Figs. 30, 33, 39, 40, 46, 51, 53, 54. 



These are double structures, which form the lateral 

 walls for the third ventricle and lie internal and posterior to 

 the corpora striata. An optic thalamus is somewhat oval 

 in shape with the long axis directed anteroposteriorly. It 

 is slightly contracted in front and below, and expanded 

 behind and above. The narrower anterior extremity is 

 the anterior tubercle, which forms the posterior boundary 

 for the foramen of Monro ; the prominent posterior part is 

 the posterior tubercle, or the pulvinar. The pulvinar 

 terminates externally in a slight oval elevation, which is the 

 external geniculate body. 



The superior surface of the optic thalamus forms a part 

 of the floor of the lateral ventricle, and furnishes support 

 for the posterior pillar of the fornix and the choroid 

 plexus. The course of the latter is indicated on the thala- 

 mus by a shallow groove, sulcus choroideus, which divides 

 the upper surface into two portions, the external being 

 within the lateral ventricle and the internal covered by the 

 velum interpositum. The internal surface forms a nearly 

 vertical wall and limits the third ventricle laterally. It is 

 divided from the superior surface by the peduncle of the 

 pineal gland which runs forward from the gland to join the 

 anterior pillars of the fornix. 



At the posterior internal part of the superior surface of 

 the thalamus, in the angle between the peduncle of the 



