530 



THE CEREBRrM. 



parieto occipital fissure, connects the superior occipital convolution with 

 the superior parietal lobule, the second unites the middle occipital and 

 angular convolution, the third often connects the same convolutions, and 

 also with them the middle temporo-sphenoidal, and i\\Q fourth connects 

 the inferior occipital with the middle or inferior temporo-sphenoidal 

 convolution. 



Fissures. — The three occipital convolutions are separated by two 

 fissures, the superior and inferior occiiyital, of which the superior is often 

 continuous with the intra-parietal. Its lower part may have a more 

 or less vertical direction, and has then been termed the transverse 

 occipital. 



The Temporo-sphenoidal lobe (fig. 370, &c.) is bounded in front 

 and above by the commencement and posterior limb of the fissure of 

 Sylvius. Behind, it is continuous with the occipital lobe. Three 

 nearly parallel convolutions can usually be distinguished; a suimior 

 bounding below the posterior limb of the Sylvian fissure, and con- 

 tinuous behind with the angular convolution, a middle continuous with 

 the angular gyrus, or middle occipital convolution, by the fourth annec- 

 tant gyrus and an inferior continuous with the inferior occipital. These 

 convolutions are separated by two Jissures, of which the superior, from 

 its relation to the Sylvian fissure has been termed the jmraUcl fissure. 

 The inferior is commonly interrupted by a secondary gyrus connecting 

 the middle and inferior convolutions. 



The Central lobe, or Island of Reil (figs. 371, 10, 12 ; fig. 376, 

 c), lies deeply within the fissure of Sylvius, being rarely visible except 

 when the lips of that fissure are separated. It is a triangular eminence 

 forming a sort of Delta between the two divisions of that fissure, and 

 consists of about six short, straight convolutions (gyri operti) which 

 radiate outwards from a point just external to the anterior perforated 



Fig. 373. 



cate 



Fig. 373. — CONVOLTTTIONS CF THE MeDIAN AND TeOTOEIAL SURFACES OP RiGHT HEMI- 

 SPHERE. From a simply Convoluted European Brain. About J 



Marg. c, marginal convolution; g. forn., gyrus fornicatus or convolution of the 

 corpus callosum ; unc. c, uncinate convolution; i. oc. -tern}?, c, inferior occipito -temporal 

 convolution ; d. c, dentate convolution ; /. Ro. , depression corresponding to the upper 

 extremity of the fissure of Rolando; par.-oc. f., parieto-occipital fissure; calc.f., cal- 

 carine fissure; coll, /,, collateral fissure ; d /., dentate fissure ; t. h. taenia hippocampi. 



