474 THE BRAIN 



terior part of the collateral fissure below. It commences at 

 the occipital pole and narrows, as it passes anteriorly, to its 

 union with the hippocampal gyrus. It lies partly on the 

 medial surface and partly on the tentorial surface of the 

 occipital lobe. 



Tentorial Surface of the Occipital Lobe. On this aspect 

 lie part of the gyrus lingualis and the posterior part of the 

 fusiform gyrus. They are separated by the posterior part 

 of the collateral fissure. The gyrus fusiformis takes part, 

 anteriorly, in the formation of the temporal lobe, and it is 

 separated from the inferior temporal gyrus by the inferior 

 temporal sulcus. 



Posterior cuneo- ^ y 3 ^Anterior part of the 



lingual deep gyrus 



FIG. 189. Posterior part of medial surface of the Left Hemisphere. The 

 calcarine and the parieto-occipital fissures are widely opened up to show 

 the deep gyri within them. 



Lateral Surface of the Occipital Lobe. There are two well- 

 marked sulci on this surface of the occipital lobe viz. the 

 sulcus occipitalis transversus and the sulcus occipitalis lateralis 

 or sulcus lunatus of Elliot Smith. 



The sulcus occipitalis transversus (Fig. 186) extends trans- 

 versely across the upper part of the lobe posterior to the arcus 

 parieto- occipitalis. It has already been described as the 

 terminal bifurcation of the ramus occipitalis of the inter- 

 parietal sulcus. 



The sulcus occipitalis lateralis (Fig. 186) is a short 

 horizontal furrow which divides the lateral surface of the lobe 

 into an upper and a lower area of very nearly equal extent. 

 These areas are connected by means of superficial annectant 

 gyri with the parietal and temporal lobes. 



