Operative surgery, for students and practitioners . an anterior horizontal, whichpasses forward into the same convolution. The parieto-occipital fissure, as seen upon the external surfaceof the cerebrum, is little more than a notch upon the inner borderof the cerebrum, and serves to mark the boundary line between theparietal and occipital lobes. The parieto-occipital fissure is wellmarked upon the inner surface of the hemisphere. 60 HEAD AND FACE. If the edges of the fissure of Sylvius are separated, that portionof the cerebrum called the island of Eeil is exposed to view. Thisarea is not cove
Operative surgery, for students and practitioners . an anterior horizontal, whichpasses forward into the same convolution. The parieto-occipital fissure, as seen upon the external surfaceof the cerebrum, is little more than a notch upon the inner borderof the cerebrum, and serves to mark the boundary line between theparietal and occipital lobes. The parieto-occipital fissure is wellmarked upon the inner surface of the hemisphere. 60 HEAD AND FACE. If the edges of the fissure of Sylvius are separated, that portionof the cerebrum called the island of Eeil is exposed to view. Thisarea is not covered in the foetus, but becomes covered over as a re-sult of the overgrowing of the frontal, parietal, and temporo- sphe-noidal lobes during the course of their development. The convolutions immediately anterior and posterior to the fissureof Eolando are called the gyrus prgecentralis and the gyrus post-centralis. The motor area corresponds to the anterior of these twoconvolutions, extending forward on to the adjacent parts of the frontal i^l-Afvr. Fig. 36.—Showing the Motor Area; Sensory Area (cutaneous and muscularsense); Stereognosis; Hearing; Speech (Speech Expression and Speech Under-standing, Vocal and V^^ritten); Vision. convolutions. The area for the arm corresponds roughly to the mid-dle third, to that portion of the convolution which lies anterior tothe concave part of the fissure of Eolando between the genu sujDeriorand the genu inferior; the portion for movements of the leg andtrunk above this area and for movement of muscles of face, tongue,etc., below this area. The third inferior frontal convolution on the left side correspondsto the center for motor speech—Brocas convolution. The areas con-cerned in other known centers are shown in the picture from Krause. The internal surface of the cerebrum is flat, presents severalfissures, and is separated from that of the opposite hemisphere bythe falx cerebri. BRAIN. 61 The inferior surface—base of the brain—rests i
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