690 



CONVOLUTIONS OF THE CEREBRUM. 



tions-superior, middle, and iufcrior-the two former being separated by the parallel sulcus, 

 while the whole lobe is mapped off from the frontal by the Sylvian fissure (S) ] 



rThe occipital lobe (tig. 479, O) is small, forms the rounded posterior end of the cerebrum 

 and is se,*ra\ol from the parietal lobe by the parietooccipital Assure which .fissure , , bridged 

 over at the lower part by the four anuectant gyn {pits de passage of Gratiolet). It has three 

 convolutions-superior (0,), middle (0 8 ), and inferior (0 3 )-on its outer surface.] . 



TThe central lobe or island of Beil, consists of five or six short, straight convolutions (gyn 

 onerti fie 481) radiating outwards and backwards from near the anterior perforated spot, 

 ami can only be seen when the margins of the Sylvian fissure are pulled asunder. The 

 operculum, consisting of the extremities of the inferior frontal, ascending parietal, and frontal 

 convolutions, lie outside it, cover it, and conceal it from view.] 



fOn the inner or mesial surface of the cerebrum are the gyrus fornicatus (ng. 480, (*t), or 

 convolution of the corpus callosum, which runs parallel to and bends round the anterior and 



Fig. 479. 



Left side of the human brain (diagrammatic). F, frontal ; P, parietal ; 0, occipital ; T, 

 temporo-sphenoidal lobe ; S, fissure of Sylvius ; S', horizontal, S", ascending ramus of S ; 

 c, sulcus centralis, or fissure of Rolando ; A, ascending frontal, and B, ascending parietal 

 convolution ; F 1? superior, F 3 , middle, and F 8 , inferior frontal convolutions ; f lf superior, 

 and / inferior frontal fissures ; / 8 , sulcus praecentralis ; P, superior parietal lobule ; P, 

 inferior parietal lobule, consisting of P 2 , supra-marginal gyrus, and P 2 ', angular gyrus ; ip, 

 sulcus interparietalis ; an, termination of calloso -marginal fissure ; lf first, 2 , second, 

 0,, third occipital convolutions ; po, parietal- occipital fissure ; 0, transverse occipital 

 fissure ; o, inferior longitudinal occipital fissure ; T 1? first, T 2 , second, T 3 , third temporo- 

 sphenoidal convolutions ; t x , first, t t , second temporo-sphenoidal fissures. 



posterior extremities of the corpus callosum, terminating posteriorly in the gyrus uncinatus or 

 gyrus hippocampi (fig. 480, H), and ending anteriorly in a crooked extremity, the subiculum 

 cornu ammonis (fig. 480, U). Above it is the calloso-marginal fissure (fig. 480, cm), and 

 running parallel to it is the marginal convolution (fig. 480), which lies between the latter 

 fissure and the margin of the longitudinal .fissure ; it is, however, merely the mesial aspect of 

 the frontal and parietal convolutions. The quadrate lobule or prsecuneus lies (fig. 480, Pi), 

 between the posterior extremity of the calloso-marginal fissure and the parieto-occipital fissure; 

 it is merely the mesial aspect of the ascending parietal convolution. The parieto-occipital 



