66 THE ANATOMY OF VERTEBEATED ANIMALS. 



01, the olfactory lobe; A., the frontal lobe ; -B., the occipital lobe ; 



C, the temporal lobe ; 8i/., the Sylvian fissure ; In., the insula ; S. Or., 

 supraorbital ; S.F., M.F., I.F.. superior, middle, and inferior frontal 

 gyri; ^.P , antero-parietal ; P.P., postero-parietal pyri ; R, sulcus 

 of Rolando; P. P/, postero-parietal lobule ; OP/'., external perpen- 

 dicular or occipito-tempnral sulcus ; An, angular gyrus; 2, .3, i. an- 

 nectent gyri ; A.T., 31. T., P.T. the three temporal, and S.Oc, 

 M. Oc, I. Oc. the three occipital gyri. 



hides the cerebellum -when the brain is viewed from above. 

 What in the Rabbit was a mere angulation at Sy, in the 

 Pig has become a long sulcus — the Sylvian fissure, the 

 lips of which are formed by a gyrus, the Sylvian, or angular, 

 gyrus. Two other sets of gyri, more or less parallel with 

 this, are visible upon the outer surface of the hemisphere ; 

 and at the entrance of the Sylvian fissure, at In, there is an 

 elevation which answers to the insula, or central lobe. 



In the Chimpanzee, the olfactory nerves, or rather lobes, 

 are, relatively, very small, and the tracts which connect them 

 with the uncinate gyri {substantia perforates) are completely 

 hidden by the temporal gyri (C). The Sylvian fissure is 

 very long and deep, and begins to hide the insula, on which 

 a few fan-shaped gyi-i are developed. The frontal lobes are 

 very large, and overlap the olfactory nerves for a long 

 distance ; while the occipital lobes completely cover and 

 extend beyond the cerebellum, so as to hide it completely 

 from an eye placed above. The gyii and sulci have now 

 attained an arrangement which is characteristic of aU the 

 highest Mammalia. The fissure of Rolando [B) divides the 

 antero-parietal gyrus (A.P) from the postero-jjarietal {P.P). 

 These two gyri, with the postero-parietal lobule {P. PL), and 

 part of the a.ngular gyi'us [An), constitute the Parietal lobe. 

 Thefrontal lobe, which lies anterior to this, the occipital lobe, 

 which lies behind it, and the temporal lobe, which lies below 

 it, each present three tiers of gyi-i, which, in the case of the 

 frontal and occipital lobes, are called superior, middle, and 

 inferior— in that of the temporal lobe, anterior, middle, 

 and posterior. The inferior surface of the frontal lobe, 

 which lies on the roof of the orbit [S. Or.), presents many 

 small sulci and gyri. 



On the inner face of the cerebral hemisphere (Kg. 22) 



