NERVOUS SYSTEM 



359 



by a deep fissure. They are connected below by a broad 

 nerve mass, the corpus callosum. 



From the under surface of the brain, the other parts can 

 be made out. The fissure continues back to the mid brain. 



Fig. 179 B. Ventral view of brain, showing origin of cranial nerves. I, 

 olfactory; II, optic; III, ocular motor; IV, patheticus; V, trigeminal; 

 VI, abducent; VII, facial; VIII, auditory; IX, glossopharyngeal; 

 X, pneumogastrie; XI, spinal accessory; XII, hypoglossal; ncl, 1st 

 spinal nerve. (After Martin.) 



The two long olfactory lobes project forward from in front 

 of the mid brain. The optic nerves arise from it. Posterior 

 to the mid brain lies the hind brain, consisting of the large 

 wrinkled lobes of the cerebellum (fig. 179 A, c), lying appar- 



