EMBRYOLOGY AND COMPARATIVE ANATOMY OF BRAIN. 



23 



corpus striatum to disappear in its depths, and, growing back- 

 ward, envelops the more posteriorly situated inter- and mid- 

 brains (in the human being the cerebellum as well). 



FIG. 15. 

 Brain of reptile. Diagram of a sagittal section. 



The cortical layer which covers the pallium at almost all 

 points must, on account of its great expanse, lie in numerous folds. 

 These are absent only in the lowest mammals (lissencephalous 



FIG. 16. 



Brain of bird. Diagram of a sagittal section. 

 Jlittelliirndach, Mid-brain roof. 



mammals). In all others they are present in more or less 

 abundance (gyrencephalous mammals). The arrangement of 

 these folds, which is constant for the separate classes of animals, 



