THE BRAIN 



173 



Tr.ojit Jkf <p 



Fio. l-ti. — Brain ov Pigeon. (A, dorsal; B, ventral; and C, lateral view. ) 



VH, cerebral hemispheres ; MH, optic lobes ; HU, cerebellum ; XH, medulla 

 oblongata ; Med, spinal cord ; I-XIl, cranial nerves ; 1 , 2, first and second 

 spinal nerves ; L.ol^ olfactory lobes ; Tr.opt, optic tract ; Jiif, infundibulum ; 

 Hyp, hypophysis. 



from above (Fig. 143) while in the higher types (Primates) even 

 part of the cerebellum is hidden (Figs. 145, 146). 



The commissures between the hemispheres (corjms callosum 

 and fornix, Fig. 145) are also much more highly develoiDed than 

 in the Sauropsida. The corpus callosum or pallial commissure, 

 though small in the lower Mammalia (e.g., Monotremes and 



