STRUCTURE OF THE CEREBRUM. 419 



other, pushes itself over; and so, again and again, with the 

 same act, rotates itself. Such movements cease when the other 

 crus cerebelli is divided ; but probably only because the paral- 

 ysis of the body is thus made almost complete. 



STRUCTURE AND PHYSIOLOGY OF THE CEREBRUM. 



The cerebrum is placed in connection with the pons and 

 medulla oblongata by its two crura or peduncles (Fig. 149) : it 

 is connected with the cerebellum, by the processes called su- 



FlG. 149. 



Plan in outline of the encephalon, as seen from the right side. y& (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, me- 

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

 peduncles of the cerebellum. 



perior crura of the cerebellum, or proeessus a cerebello ad testes, 

 and by a layer of gray matter called the valve of Vieussens, 

 which lies between these processes, and extends from the in- 

 ferior vermiform process of the cerebellum to the corpora quad- 

 rigemina of the cerebrum. These parts, which thus connect 

 the cerebrum with the other principal divisions of the cerebro- 

 spinal nervous centre, form parts of the walls of a cavity (the 

 fourth ventricle) and a canal (the iter a tertio ad quartum ven- 



