1392 A MANUAL OF ANATOMY 



of the posterior limb of the fissure of Sylvius, and (2) a line pro- 

 longing this limb backwards to meet the posterior boundary of the 

 parietal lobe. Anteriorly it is bounded by the stem of the fissure 

 of Sylvius, which separates it from the orbital area of the frontal 

 lobe. Posteriorly it is continuous with the occipital lobe, but the 

 separation may be indicated by the following lines : externally by 

 a line connecting the extremity of the external part of the parieto- 

 occipital fissure with the pre-occipital notch, and inferiorly by a 

 line connecting the pre-occipital notch with the portion of the limbic 

 lobe which lies below the splenium of the corpus callosum (isthmus 

 of the limbic lobe). Inferiorly it is separated from the hippocampal 

 gyrus by the collateral fissure. The temporal lobe is somewhat 

 pyramidal, the rounded apex being directed forwards. The apical 

 part forms the temporal pole, and it overhangs from behind the 

 stem of the fissure of Sylvius. The uncus of the hippocampal gyrus 

 lies on its inner side, but on a more posterior level, and separated 

 from it by the temporal sulcus. 



The lobe presents three surfaces — superior, external, and inferior. 



The superior or opercular surface is concealed within the fissure 

 of Sylvius, and is directed towards the island of ReU. 



The external surface presents two horizontaJ sulci and three 

 convolutions, the latter being disposed in horizontal tiers. 



The sulci are called first temporal and second temporal, 

 respectively. The first temporal sulcus is parallel to the posterior 

 limb of the fissure of Sylvius, from which circumstance it is called 

 the parallel sulcus. It commences near the temporal pole, and 

 posteriorly it turns upwards into the parietal lobe, where the 

 angular gyrus arches round it. The second temporal sulcus is 

 parallel to the first, below which it lies, and it is usually broken 

 up into two or more parts by annectant gyri. Posteriorly it turns 

 upwards into the parietal lobe, where the postparietal gyrus curves 

 round it. 



The gyri of the external surface, as stated, are arranged in hori- 

 zontal tiers, and are three in nimiber, first, second, and third, in 

 this order from above downwards. 



The first temporal gyrus is situated between the posterior limb 

 of the fissure of Sylvius and the parallel sulcus. Posteriorly it is 

 continuous with the supramarginal, and slightly with the angular, 

 gyri of the parietal lobe. The second temporal gyrus lies between 

 the parallel and second temporal sulci, and posteriorly is continuous 

 with the angular and postparietal gyri of the parietal lobe. The 

 third temporal gyrus lies below the second temporal sulcus, and 

 posteriorly is continuous with the lower part of the external surface 

 of the occipital lobe. 



The inferior or tentorial surface of the temporal lobe presents the 

 occipito-temporal sulcus and the occipito-temporal gyrus. The 

 occipito-temporal sulcus extends from before backwards, lying near 

 the infero-lateral margin of the hemisphere, and external to the 

 collateral fissure. It is usually broken up into parts by annectant 



