CEREBRUM. 



585 



CEREBRUM. 



UPPER SURFACE. (Fig. 328.) 



The Cerebrum, in man, constitutes the largest portion of the encephalon. Its 

 upper surface is of an ovoidal form, broader behind than in front, convex in its 

 general outline, and divided into two lateral halves or hemispheres, right and 

 left, by the great longitudinal fissure, which extends throughout the entire length 

 of the cerebrum in the middle line, reaching down to the base of the brain in 

 front and behind, but interrupted in the middle by a broad transverse commis- 

 sure of white matter, the corpus callosum, which connects the two hemispheres 

 together. This fissure lodges the falx cerebri, and indicates the original de- 

 velopment of the brain by two lateral halves. 



Fig. 328. Upper Surface of the Brain, the Pia Mater having been removed. 



Gi-eat LonffituJlnaT Fissur* 



Each hemisphere presents an outer surface, which is convex, to correspond 

 with the vault of the cranium ; an inner surface, flattened, and in contact with 

 the opposite hemisphere (the two inner surfaces forming the sides of the longi- 

 tudinal fissure) ; and an under surface or base, of more irregular form, which 

 rests, in front, on the anterior and middle fossa at the base of the skull, and 

 behind, upon the tentorium. 



Convolutions. If the pia mater is removed with the forceps, the entire surface 

 of each hemisphere will be seen to present a number of convoluted eminences, 

 the convolutions separated from each other by depressions (sulci) of various 

 depths. The outer surface of each convolution, as well as the sides and bottom 



