BRAIN 



From the primitive fore -brain are differentiated a posterior 

 diencephalon (thalamencephalon) and an anterior secondary fore- 



JZ"' 



FIG. 8. 



\~ Dorsal view of the brain of Heptanehus cinereus. (From Gegenbaur, Vergl. Anat. Wirbclticre.) 

 Ac, aiulitory nerve; F, facial, Gp, glossopharyugeal ; H, cerebellum; M, optic lobe ; Ms, spinal 

 cord ; A', medulla, also nasal sac ; 0, optic nerve ; Po, olfactory tract ; Tr, trigeminal nerve ; 

 V, fore-brain ; Vg, vagus nerve ; Z, diencephalon ; a and b, branches of facial and trigeminal ; 

 ab, abducens ; Tip, (hypoglossal) occipito-spinals ; I, olfactory lobe ; om, oculomotor ; v, origin 

 of vagus roots. 



brain, the telencephalon. The diencephalon, bounded behind by the 

 posterior commissure, is crossed above by the superior commissure 



