THE BRAIN 



167 



relatively larger than in other Amphibians, and the hemispheres 

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

 A 



-ME 



BE 



KZH-^ 



-MR 



C 



W ZEMH JV niiNn 



Med, 



ETro;piM Em 



Fig. 137. — Bkain op Rana esculenta. (A, dorsal ; B, ventral; and C, 

 lateral view. ) 



VH, cerebral hemispheres ; Zff, thalamencephalon ; MJI, mid-brain ; HII, cere- 

 bellum ; NH, medulla oblongata ; 31ed, 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 ; +, space between 

 the two hemispheres; IV.opt, 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 partsoverlie one another to a greater extent, especially 

 in the Agamse and Ascalabotte. 



