502 



COLLEGE ZOOLOGY 



hypophysis ( Hyp) are visible only on the ventral surface of the 

 brain. 



The functions of the different parts of the frog's brain have 

 been partially determined by experiments in which the parts 

 were removed and the effects upon the animals observed. It is 



oZ. lobe 



cerebrum 



zn 



ZU Tr.opt 

 Jnj 



optic lobe 



cerebellum 



medulla 



ol. lobe 



33. II -M* 



FIG. 422. Brain of the frog. A, dorsal aspect. B, ventral aspect. 

 I-XII, nerves; Hyp, hypophysis; Jnf, infundibulum; Med, Nil, medulla 

 oblongata; Tr.opt, optic tract; ZH, diencephalon. (From Davenport, after 

 Wiedersheim.) 



not certain what the functions of the cerebral hemispheres are 

 in the frog. They are the seat of intelligence and voluntary 

 control in higher animals. When the midbrain is removed 

 along with the cerebral hemispheres, the frog loses the power 

 of spontaneous movement. When the optic lobes are removed, 

 the spinal cord becomes more irritable; this shows that these 



