THE CEREBRUM. 533 



They may, therefore, be regarded as the continuation of 

 the cerebro- spinal axis or column ; on which, as a develop- 

 ment from the simple type, the cerebellum is placed ; and, 

 on the further continuation of which, structures both larger 

 and more numerous are raised, to form the cerebrum 

 (fig. 142). 



Fig. 142.* 



The cerebral convolutions appear to be formed of nearly 

 parallel plates of fibres, the ends of which are turned 

 towards the surface of the brain, and are overlaid and 

 mingled with successive layers of grey nerve-substance. 

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



* Fig. 142. 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 connections. 

 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 pedun- 

 cles of the cerebellum. 



