198 DISSECTION OF THE BRAIN. 



Internal perpendicular or parieto-occipital fissure (PO, fig. 02) sepa- 

 rates the two preceding lobules. Continuous with the external fissure of 

 the same name, it opens below into the following. 



The calcarine sulcus /, (Huxley) is directed across the back of the 

 hemisphere below the level of the corpus callosum, and ends in front at 

 the gyms fornicatus ( l8 ), whose hinder limit it marks. It receives above 



62. 



PO 



TS 



CONVOLUTIONS AND FISSURES ON THE INNER FACE OF THE HEMISPHERE. 



P. 0. Internal parieto-occipital fissure. 18. Convolution of corpus callosum. 



Cat. Corpus callosum, cut. 18'. Quadrilateral lobule. 



i. Calloso-marginal sulcus. 19. Uncinate gyrns. 



L Calcarine sulcus. 19'. Crotchet or hook of the uncinate gyrus. 



m. Dentate sulcus. 25. Occipital lobule. 



n. Collateral sulcus. 9. Inferior temporo-sphenoidal gyrus partly 

 17. Marginal gyrus. seen. 



the internal perpendicular fissure; and it sinks into the posterior cornu of 

 the lateral ventricle, forming the eminence of the hippocampus minor. 



Internal temporo-sphenoidal convolutions (fig. 62) are two in number, 

 viz., the uncinate and dentate, and occupy the tentorial surface of the 

 hemisphere. 



The uncinate or hippocampal convolution ( 19 ) is prolonged from the 

 posterior end of the hemisphere nearly to the tip of the temporo-sphenoidal 

 lobe. It is somewhat narrowed in the middle, where the gyrus fornicatus 

 blends with it ; and is enlarged at each end, especially at the posterior 

 where it is subdivided by sulci. Below it is a long curved sulcus, the 

 collateral (11} ; and above it are the calcarine (/), and the dentate sul- 

 cus (m). From the anterior extremity a narrow part ( 19/ , uncus) is pro- 

 longed back for half an inch on the inner side, like a hook. 



Below the uncinate convolution is part of the inferior temporo-sphe- 

 noidal convolution ( 9 ), before described, which forms the lower edge of 

 the temporo-sphenoidal lobe, appearing more largely on the inner than 

 on the outer face. 



The collateral sulcus n, (Huxley) courses along the lower border of the 

 uncinate convolution ; it projects into the inferior cornu of the lateral 

 ventricle) and gives rise to the prominence of the eminentia collaterals. 

 Secondary sulci emanate from it, and it is often interrupted by cross 



The dentate sulcus m, (Huxley) is the deep groove at the upper edge of 

 the uncinate convolution ( 19 j, and corresponds with the prominence of the 



