196 



DISSECTION OF THE BRAIX. 



the ascending convolution, and is continued back along the upper margin 

 of the hemisphere as far as the parieto-occipital fissure. Subdivided on the 

 surface into two chief parts it is joined behind to the occipital lobe by the 

 small annectant gyrus (a). To its outer side lies the upper part of the 

 intraparietal sulcus ; and here it joins usually the following convolution, A. 

 The supra- marginal convolution A, lying outside and below the preced- 

 ing, is interposed between the intraparietal sulcus, / P, and the Sylvian 

 fissure (outer end). Variable in shape it joins, below, the ascending 

 parietal convolution ( 5 ) ; it may communicate above with the parietal 

 lobule, and behind with the following. 



The angular convolution ( 6 ), very complicated and not well defined, is 

 placed at the extremity of the hinder limb of the Sylvian fissure, and is 



composed of two or three pieces 



Fig. 61. Above it is the parietal lobule ; 



and below, the temporo-sphenoidal 



j^^ ^-^ lobe which it joins. In front lies 



Y \ \ \ the supra-marginal convolution ; 



and behind, the occipital lobe, with 

 which it blends by the small annect- 

 ant gyrus (b). 



c. The occipital convolutions (fig. 

 60) are small and very much di- 

 vided, so that their outline is un- 

 certain. They are three in number, 

 lying one above another, and sepa- 



II 2 x rated by sulci, something like the 



II ' J|ilWt- -A frontal gyri at the opposite end of 



J\ ~ 



J*^^~ v 1 The "I'P 61 * ( 10 )' f rmin g P art 



the margin of the longitudinal fis- 

 sure, receives an annectant gyrus 

 from the parietal lobule. 



The middle ( n ), crossing out- 

 wards the hemisphere, has two an- 

 nectant gyri to other convolutions ; 

 one (b) joining it above to the an- 

 gular convolution, and another (c) 

 passing to the middle temporo- 

 sphenoidal convolution. 



The inferior ( 12 ) occupies the tip 

 of the hemisphere between the up- 

 per and under surfaces. At the 

 inner end it is continuous with the 

 upper gyrus ; and at the outer end 

 with the interior temporo-sphenoi- 

 dal convolution ( 9 ) by an annectant 

 gyrus (d). 



d. The temporo-sphenoidal convolutions (fig. GO), three in number, run 

 from above down, and are separated from one another by two sulci. 



The superior ( 7 j bounds posteriorly the horizontal limb of the Sylvian 

 fissure. At the upper end it is connected by a gyrus with the angular 

 convolution. 



The middle ( 8 ) is separated from the first by the parallel sulcus (P). 



VIEW OF THE ORBITAL LOBULE AND THE 

 CENTRAL LOBE. 



C. Island of Reil or median lole. 



0. Olfactory sulcus. 



2. Internal ; and 



6. External orbital convolution. 



posterior ; 

 17. Marginal convolution of the hemisphere 



