226 A MANUAL OF ANATOMY. 



is a small oval nucleus with its long axis placed trans- 

 versely. Figs. 53, 54. 



The external geniculate body is described as an en- 

 largement at the outer portion of the pulvinar, with which 

 it is continuous. See Optic thalami, page 230. 



DISSECTION. 



One half of the cerebrum should now be carefully sectioned horizontally, 

 and the other half transverse-vertically as far as the beginning of the aqueduct 

 of Sylvius. From these sections study the situation, shape, and relations of 

 the basal ganglia and nerve pathways. 



The Corpora Striata. (Study carefully all the various 

 sections, especially Figs. 30, 33, 35, 37, 43, 44, 51.) 



These are symmetrical ovoid elevations of gray matter, 

 which project into the floor of the lateral ventricles. 



A corpus striatum, by consulting the various sections, 

 will be seen to consist of an oval form with a long axis 

 placed anteroposteriorly. It is located internal to and 

 opposite the central lobe of the cerebrum. It reaches to 

 and forms the base of the brain corresponding to the 

 anterior perforated space, and extends into the cavity of the 

 lateral ventricle as the caudate nucleus. It will be seen to 

 consist of two masses of gray matter separated from each 

 other by a sheet of white fibres, except at their extreme 

 anterior inferior portion. 



The two gray masses are the caudate and lenticular 

 nuclei, the white fibres which separate them the internal 

 capsule. 



The Caudate Nucleus. This is the inner and superior 

 (also anterior and posterior) band of gray matter which lies 

 within the lateral ventricle, and hence is the intraventricu- 

 lar portion of the corpus striatum. It is wider in front, 

 where it forms a prominent elevation in the anterior horn, 





