726 



THE NERVOUS SYSTEM. 



tinct than the upper surface, and has on each side of it, marking it off from the 

 hemisphere, a, deep groove which runs antero-posteriorly. The inferior surface of 

 the worm can be seen as a whole only after removal of the pons and medulla. 

 The space or fossa between the inferior surfaces of the hemispheres, and which con- 

 tains the inferior worm, is called the vallecula, and the grooves above mentioned, 

 one on each side of the lower surface of the worm, are known as the sulci vallec- 

 ulce. The upper or anterior part of the vallecula lies dorsal to the medulla, and 

 is continued upward into the anterior cerebellar notch; the lower or posterior 



Sup. Fed. of Cerebel. 

 Mid. Fed. 



Inf. Fed. 



Great Horiz. Fissure 

 FIG. 426. Under surface of the cerebellum. 



part contains the lower portion of the falx cerebelli, and is continued into the 

 posterior cerebellar notch (see below). 



Although in the adult human brain each hemisphere is much larger than the 

 worm, still the latter is morphologically the more important, being the part first 

 developed in mammals, and, in many of them lower than man, constituting a large 

 median lobe quite distinct from the hemispheres. Furthermore, in fishes and 

 reptiles it is the only part which exists, the hemispheres being additions and 

 attaining their maximum size in man. 



The Notches of the Cerebellum. The hemispheres are separated in front in the 

 middle line by a deep notch, the anterior cerebellar notch (incisura cerebelli ante- 



Incimira 



cerebelli posterior. 

 FIG. 427. Upper surface of the cerebellum. 



rior\ and also behind (similarly) by a smaller notch, posterior cerebellar notch 

 ineisura cerebelli posterior] (Fig. 427). The anterior notch is much wider, and 



