THE BRAIN 



167 



relatively larger than in other Amphibians, and the hemispheres 

 overlap the posterior parts of the brain to a larger extent. 

 A 





FIG. 137. BRAIN OF Rana escuhnta. (A, dorsal ; B, ventral; and C, 

 lateral view.) 



VH, cerebral hemispheres ; ZH, thalamencephalon ; MH, mid-brain ; HIT, cere- 

 bellum ; ^H, medulla oblongata ; Med, spinal cord ; I-X, cranial nerves ; 

 la, lateral root of olfactory nerve ; XII (1), ventral root of first spinal nerve 

 (hypoglossal), and 1, its dorsal root ; L.ol, olfactory lobe ; t, space between 

 the two hemispheres ; Tr.oj)t, optic tract ; Jnf, infundibulum ; Hyp, 

 hypophysis. 



Reptiles. The brain of Reptiles reaches a considerably higher 

 stage of development than that of the forms already described, and 

 the individual parts overlie one another to a greater extent, especially 

 in the Again a3 and Ascalabotse. 



