484 THE BRAIN 



part of the vermis forms a median ridge, from which the 

 surface slopes gradually downwards, on each side, to the margin 

 of the corresponding hemisphere. On the upper part of the 

 vermis four regions are recognised. Anteriorly, at the posterior 

 end of the anterior notch, lies the central lobe, and prolonged 

 upwards from it on the dorsal surface of the anterior medullary 

 velum, between the brachia conjunctiva, are a few folia which 

 constitute the lingula. Posterior to the central lobe is the 

 monticulus, separable into two parts an anterior, more elevated 

 portion, the culmen, and a posterior, sloping ridge, the declive. 

 Posterior to the declive, in the anterior boundary of the 

 posterior notch, lies a single folium called the folium vermis. 



On the inferior surface of the cerebellum, the distinction 

 between the three constituent parts of the organ is much 

 better marked. On that aspect the hemispheres are full, 

 prominent and convex, and they are separated by a deep, 

 median hollow which is continued forwards from the posterior 

 notch. The hollow is termed the vallecula cerebelli, and in its 

 anterior part the medulla oblongata is lodged. If the medulla 

 is forced away from the cerebellum, and the hemispheres 

 are pulled apart so as to expose the upper boundary of the 

 vallecula, it will be seen that that boundary is formed by the 

 inferior surface of the vermis, and, further, that the vermis is 

 separated, on eajch side, from the corresponding hemisphere 

 by a distinct furrow, termed the sulcus valleculcel 



If the margin of the vermis, where it forms the posterior 

 boundary of the anterior notch on the superior aspect of 

 the cerebellum, is gently raised, and at the same time the 

 mesencephalon is pulled forwards, two strands lying upon 

 the dorsal aspect of the pons will be seen. These are 

 the brachia conjunctiva cerebelli (O.T. superior peduncles]. 

 They emerge from the white matter of the cerebellum, 

 converge as they proceed upwards, and, finally, they dis- 

 appear under the inferior quadrigeminal bodies. The thin 

 lamina which is stretched across between them is the anterior 

 medullary velum. It is continuous below with the white core 

 of the vermis, and it helps to form the roof of the upper 

 part of the fourth ventricle. From its dorsal surface, close 



1 As the medulla oblongata is displaced forwards, and the hemispheres of 

 the cerebellum are pulled apart, the epithelial roof of the fourth ventricle and 

 its covering of pia mater will be torn away, and the lower part of the floor 

 or anterior boundary of the fourth ventricle will be displayed. 



