THE CEREBRUM. 205 



tinuous above with the anterior frontal, and below with the inferior 

 frontal, convolution. 



The superior frontal convolution is bounded internally by the longi- 

 tudinal fissure, and externally by the superior frontal fissure ; it is 

 connected with the superior end of the frontal convolution, and runs 

 downward and forward to the anterior extremity of the frontal lobe, 

 where it turns backward, and rests upon the orbital plate of the 

 frontal bone. 



The middle frontal convolution, the largest of the three, runs 

 from behind forward, along the sides of the lobe, to its anterior 

 part ; it is bounded above by the superior and below by the inferior 

 frontal fissures. 



The inferior frontal convolution winds around the ascending 

 branch of the fissure of Sylvius, in the anterior and inferior portion 

 of the cerebrum. 



Parietal Lobe. The ascending parietal convolution is situated just 

 behind the fissure of Rolando, running downward and forward ; 

 above, it becomes continuous with the upper parietal convolution, and 

 below, winds around to be united with the ascending frontal. 



The upper parietal convolution is situated between the parietal 

 and longitudinal fissures. 



The supramarginal convolution winds around the superior extremity 

 of the fissure of Sylvius. 



The angular convolution, a continuation of the preceding, follows 

 the parietal fissure to its posterior extremity, and then makes a 

 sharp angle downward and forward. 



Temporosphenoid Lobe. Contains three well-marked convolutions, 

 the superior, middle and inferior, separated by well-defined fissures, 

 and continuous posteriorly with the convolutions of the parietal lobe. 



The occipital lobe lies behind the parieto-occipital fissure, and 

 contains the superior, middle and inferior convolutions, not well 

 marked. 



The central lobe, or island of Reil, situated at the bifurcation of 

 the fissure of Sylvius, is a triangular-shaped cluster of six convolu- 

 tions, the gyri operti, which are connected with those of 'the frontal, 

 parietal, and temporosphenoid lobes. 



Upon the inner or mesial aspect of the hemisphere are found 

 (Fig. 25) 



