242 NERVOUS SYSTEM. 



FIG. 99. 



fundibulum (99. A. e,) like the hypophysis of a reptile, is 

 more broad and extended ; the corpora quadrigemina are 

 larger and less covered by the hemispheres, and the trans- 

 verse sulcus divides them more posteriorly than in the lion, 

 (99. B.) This transverse sulcus is wanting on the optic 

 lobes of the ornithorhyncus, where they are nearly as smooth 

 and undivided as those of a bird, and its cerebral hemi- 

 spheres are destitute of convolutions, like those of many 

 rodentia, edentata, and marsupialia. The broad cerebral he- 

 mispheres of the lion are surpassed in lateral extension by 

 those of the seals, and these parts in the dolphin surpass 

 those of all the other mammalia by their great breadth and 

 by the number of their superficial convolutions. But in none 

 of these animals are the cerebellic hemispheres entirely covered 

 by the extension backwards of the cerebral, till we ascend to 

 the higher quadrumana, where we find in the pithed, or 

 orangs, almost every other character of the human spino-cere- 

 bral axis already distinctly developed, as the hippocampus 

 minor and posterior cornu of the lateral ventricles, the deep 

 cerebral convolutions and numerous cerebellic laminae, 

 the cineritious substance of the corpora olivaria and the 

 large corpora dentata, or ganglionic nuclei of the cerebellic 

 hemispheres. 



