THE FOREBRAIN 353 



(k) The parts of the metathalamus are distinguishable ex- 

 ternally as two rounded projections of the lateral surface 

 at each side of the thalamic region. One of them, the 

 lateral geniculate body (corpus geniculatum laterale), lies 

 external to the lateral thalamic tubercle, marked off from 

 it superficially only by a faint depression, and constitutes 

 the most lateral part of the thalamic mass. It contains the 



Fig. 117. Transverse section of the .forebrain passing through the inter- 

 ventricular foramina. The drawing represents a section stained by the method 

 of Weigert, which gives the white nerve fibres a dark colour. The large mass 

 of fibres dividing the corpus striatum into dorsal (nc) and ventral (gp+pu) parts 

 (the internal capsule) contains the fibres which form the basis of the cerebral 

 peduncle and the pvramid further back. 



cc, corpus callosum; ch, optic chiasma; clip, hippocampal commissure; 

 cpl, chorioid plexus of lateral ventricle; cpt, chorioid. plexus of third ventricle, 

 f, fornix; fi, interventricular foramen; fl, limbic fissure; flc, longitudinal cerebral 

 fissure; gp, part (globus pallidus) of corpus striatum; h, tapering anterior end 

 of hippocampus; ha, habenula, anterior tip; hy, hypothalamus; Ip, pynform 

 lobe; nc, part (caudate nucleus) of corpus striatum; p, cerebral cortex; pu, part 

 (putamen) of corpus striatum; sm, stria meduUaris thalami; tol, olfactory tract; 

 vl, lateral ventricle; vt, third ventricle. 



vestibule of the hemisphere for visual impulses. The 

 medial geniculate body is less prominent and occupies a 

 position immediately medial and posterior to the lateral 

 geniculate body. It relays auditory excitations to the 

 cerebral cortex. 

 (/) The optic tract (tractus opticus) passes obliquely over the 

 lateral surface of the brain from the ventrally situated 

 optic chiasma to the lateral geniculate body, part of it 



