122 ANATOMY. 



Central Lobe, or Island of Reil, lies in the fissure of Sylvius, covered by the 



frontal and temporo-sphenoidal lobes. 

 Longitudinal Fissure, separating the two hemispheres. 

 Fissure of Sylvius, at the base of the brain, extending outwards on each 



side, and dividing into 2 branches, an ascending and a horizontal one. 



It lodges the middle cerebral artery. 



Fissure of Rolando, on the superior surface, extending from the longitudi- 

 nal fissure about its centre, downwards and forwards towards the fissure 



of Sylvius, separating the frontal and parietal lobes. 

 Parieto-occipital Fissure, extends from the longitudinal fissure outwards for 



about an inch between the parietal and occipital lobes. It is better 



marked in a longitudinal section of the brain. 

 Calloso-marginal Fissure, above the gyrus fornicatus on the inner surface of 



the hemisphere. 

 Transverse Fissure, between the middle lobe and the crus cerebri, at the 



base of the brain. It admits the pia mater to the lateral ventricle. 

 Calcarine Fissure, also seen on the inner surface, extending from the lower 



end of the parieto-occipital fissure outwards to the posterior border of the 



occipital lobe. 

 First Temporo-sphenoidal Fissure, below the fissure of Sylvius, on the lateral 



surface of the brain. 



Name the principal Convolutions of the Cerebrum. The superior 

 and inner. surfaces of each hemisphere are formed of convolutions (gyri} with 

 intervening furrows (sulci) of various depths, both gyri and sulci being formed 

 of gray matter thus arranged to enable it to present a great extent of surface. 

 The convolutions are not uniform in all brains as to arrangement, nor are they 

 symmetrical in the two hemispheres. The most constant are the following : 

 Gyrus Fornicatus, the convolution over the corpus callosum, seen on the 



inner surface, arching from before backwards. 



Convolution of the Longitudinal Fissure, along the edge of that fissure on 

 the superior surface, curving over the front and back of each hemisphere, 

 to the base of the brain. 



Ascending Frontal, lies in front of the fissure of Rolando. 

 Ascending Parietal, lies behind the fissure of Rolando. 



Angular Gyrus, or PR Courbe, around the posterior end of the first temporo- 

 sphenoidal fissure. 



Many other convolutions are named by writers on the localization of cere- 

 bral functions, such as the temporo-sphenoidal, occipital, supra-marginal con- 

 volutions, etc. Their names will be found sufficiently explanatory of their 

 several locations. The Cuneus, Precuneus, and Paracentral Lobule are names 



