532 



THE NERVOUS SYSTEM. 



mingled with successive layers of grey nerve-substance. 

 The external grey matter is so arranged in layers, that a 

 vertical section of a convolution, according to Mr. Lockhart 



Fig. 149.* 



Clarke, generally presents the appearance of seven layers 

 of pale and dark nervous substance. The structure of the 

 grey matter is that which belongs to vesicular nervous 

 substance (p. 473). 



It is nearly certain that the cerebral hemispheres are 

 the organs by which, ist, we perceive those clear and 

 more impressive sensations which we can retain, and 



* Fig. 149. Plan in outline of the encephalon, as seen from the right 

 side. }. (From Quain). The parts are represented as separated from 

 one another somewhat more than natural, so as to show their connec- 

 tions. A, cerebrum ;/, g, h, its anterior, middle, and posterior lobes]; 

 e, fissure of Sylvius ; B, cerebellum ; C, pons Varolii ; D, medulla 

 oblongata ; a, peduncles of the cerebrum ; b, c, d, superior, middle, 

 and inferior peduncles of the cerebellum. 



