212 



DISSECTION OF THE BRAIN. 



UPPER SURFACE. On the upper aspect the cerebellum is raised in the 

 centre (fig. 68), but slopes towards the circumference. There is not any 

 median sulcus on this surface ; and the halves are united by a central con- 

 stricted part the superior vermiform process. Separating the upper from 

 the under surface, at the circumference, is the horizontal fissure, which is 

 wide in front, and extends backwards from the pons Varolii to the middle 

 line of the cerebellum. 



The UNDER SURFACE is convex, being received into the fossae of the 

 base of the skull, and is divided into hemispheres (fig. 66) by a median 

 hollow (vallecula). 



Fig. 66. 



UNDER PART OF THE CEREBELLUM, SEEN FROM BEHIND, THE MEDULLA OBLONOATA, 6, " b- 



BEING CUT AWAY IN GREATER PAKT. U 



a. Pons Varolli. c to e. Inferior vermiform process, consisting 



6. Medulla oblongata, cut through. of; c. Uvula, d. Pyramid, e. Com- 



missnral laminae. 



LOBES OF EACH HALF OF THE CEREBELLUM ON THE UNDER SURFACE. 

 /. Snbpeduncular. k. Posterior. 



g. Amygdaloid. 3 Third nerve attached to the crus cerebri. 



h. Biventral. 6. Two roots of the fifth nerve attached to the 



i. Slender. side of the pons Vavolii. 



The central fissure, or the vallecula, is wider at the middle than at either 

 the anterior or the posterior end, and receives the medulla oblongata. In 

 the bottom of the fissure is a mass named inferior vermiform process (fig. 



66, c to e), which corresponds with the central part connecting the halves 

 of the cerebellum on the upper surface. The two vermiform processes 

 constitute the general commissure of the halves of the cerebellum. 



Constituents of the rermiform process. In the inferior vermiform pro- 

 cess are the following eminences, which may be easily separated from one 

 another with the handle of the scalpel : Most anteriorly is a narrow body, 

 the uvula (fig. 66, e), which is named from its resemblance to the same 

 part in the throat ; it is longer from before backwards than from side to 

 side, and is divided into lamina?. Its anterior projection into the fourth 

 ventricle is named nodule, or laminated tubercle (fig. 67) ; and on the side 

 is a band of gray matter with ridges and sulci, the furrowed band (fig. 



67, rf), which unites it with the almond-like lobe of the hemisphere. 

 Connected with the nodule is a thin white layer, the medullary velum 



