FISSURE OF SYLVIUS. 141 



Fig. 101. VlEW, FROM THE SIDE AND SLIGHTLY FROM ABOVE AND BEHIND, OF, THE RIGHT HEMISPHERE 

 OF A SIMPLY CONVOLUTED EUROPEAN BRAIN. (E. A. S. ) 



Fig 102. MESIAL ASPECT OF THE LEFT HEMISPHERE OF A SIMPLY CONVOLUTED EUROPEAN BRAIN. 



(E. A. S.) 



Fig. 103. UNDER SURFACE OF A SIMPLY CONVOLUTED EUROPEAN BRAIN. (E. A. S.) 



The above are depicted nearly of the natural size. They have been drawn from photographs, and are 

 all taken from different specimens. 



The sulci are marked with small italic letters ; the gyri with italic capitals. The corresponding 

 parts are marked similarly in the three figures, 



Fig. 101. Sulci Ro., Rolandic or central; g, its superior genu ; Sy. a, anterior limb of Sylvian 

 (x, ascending part, y, horizontal part) ; Sy. p, posterior limb of Sylvian ; Sy. p. asp., ascending ramus 

 of posterior limb ; / 1} superior frontal ; / 2 , inferior frontal ; / 3 , middle frontal ; / 4 , paramesial frontal ; 

 d, diagonal, placed in this instance rather low down, and communicating with the Sylvian ; p.o. ir>f, 

 inferior precentral ; p. c. i. ant. , its anterior ramus ; p. c. sup. , superior precentral ; p. c. m , mesial precentral ; 

 p.fl. tr., transverse precentral ; rtc. tr., transverse retro-central ; i.-p. inf, intra-parietal, pars inferior 

 (inferior postcentral) ; i.-p. sup., intraparietal, pars superior (superior postcentral); i.-p. post. s. hor.. 

 intraparietal, pars posterior seu horizontal! s ; i.p. j)ost., intraparietal, pars posterior (paroccipital of 

 Wilder); i.-p. pr. asc., an ascending branch of the intraparietal; p.-o., parieto-occipital ; occ. ant., 

 anterior occipital ; occ . lat. , lateral occipital ; cole. , posterior end of calcarine ; t x , first temporal or 

 parallel; t l asc., its posterior ascending extremity, detached; < 2 , second temporal; t z asc., its 

 posterior ascending extremity joined to and apparently continuous with the first temporal. 



Gyri F lt F n , F 3 , first, second and third (superior, middle, and inferior) frontal; a, posterior part 

 of third frontal ; b, middle part (pars triangularis) ; c, orbital part ; A.F., ascending frontal ; A. P., 

 ascending parietal ; r l\, T z , T 3 , first, second, and third temporal. 



Fig. 102. Sulci Ro., upper end of Rolandic ; p.c.m., mesial precentral ; f s , mesial frontal ; 

 a.m., calloso-marginal ; pr. I., prelimbic (anterior end of calloso-marginal) ; pr. I. asc., an ascending 

 branch of the prelimbic ; pamcentr., paracentral (posterior end of calloso-marginal) ; p. I. , post-limbic ; 

 ?v). rostral; ro. inf., inferior rostral; p.-o., parieto-occipital ; calc. ant., stem of calcarine; cole, post., 

 posterior part of calcarine ; 1,2, 3, 4, places where annectent gyri occur in calcarine and parieto-occipital 

 fissures; t z , third temporal ; coll.. collateral or fourth temporal; h (placed on the fascia dentata) has 

 the hippocampal fissure just below it. 



Gyri F lt marginal part of first frontal; C, callosal (gyrus fornicatus) ; H, hippocampal; unc., 

 its uncus ; 7i, dentate; T, fourth temporal (fusiform lobule); T 5 , fifth temporal or infracalcarine 

 (lingual lobule). 



c.c, corpus callosum ; spl., its splenium ; g, its genu ; r, its rostrum ; fo, fornix ; fi., fimbria. 



Fig. 103. Sulci orb., orbital (sagittal rami) ; o.tr., transverse orbital ; olf., olfactory; x , 2 , t 3 , 

 first, second, and third temporal; coll. , collateral (fourth temporal) ; calc., calcarine. 



Gyri R, gyrus rectus ; 7\, T 3 , '1\, T s , first, third, fourth and fifth temporal ; H, hippocampal ; 

 s. r. a. , substantia reticularis alba ; unc. , uncus. 



cJi, chiasma ; s.p.a., substantia perforata antica ; i.e., tuber cinereum ; m, corpora mamillaria, 

 accidentally separated from one another in the preparation ; cr, crusta ; tin, tegmentum ; spl., splenium 

 of callosum. 



Fissure of Sylvius. The most distinct fissure in the adult brain, and also the 

 first one to make its appearance in the development of the embryo, is the fissure of 

 Sylvius. This deep and conspicuous fissure is seen at the base of the brain, opening 

 out as the vallecula Sylvii (Broca) on to the anterior perforated space. From this 

 origin the fissure passes transversely outwards to the lateral surface of the hemisphere, 

 where it presently gives off a short horizontal branch (about 2 centimeters long), 

 and a rather longer ascending branch (about 8 centimeters), the fissure being then 

 continued nearly horizontally as the posterior limb for a considerable distance (8 or 9 

 centimeters) obliquely backwards and upwards in the direction of the parieto- 

 occipital fissure, having a slightly curved course. It ends at about the junction of 

 the middle and posterior thirds of the lateral surface (midway from superior to 

 lateral border), usually by bifurcating, one branch passing obliquely upwards, the 

 other backwards and somewhat downwards. If the lips of the Sylvian fissure are 

 separated, the island of Reil is seen at the bottom of the sulcus. In section this 

 fissure, together with the limiting sulcus of the island, forms a T-shaped figure (fig. 95). 

 Its bounding convolutions are folded over the island of Reil, and the upper bounding 

 convolutions which belong partly to the parietal, partly to the frontal lobe, form the 

 operculum of Burdach. 



