GENERAL FEATURES 367 



anteriorly by the temporal pole, posteriorly by the occipital 

 pole ; laterally by the infero-lateral border, which separates it 

 from the supero-lateral surface; medially, in the posterior 

 part of its extent, by the medial occipital border, which 

 separates it from the medial surface, and, more anteriorly, by 

 a fissure called the chorioidal fissure, which lies between it and 

 the sublentiform portion of the hemisphere. 



Upon the part which rests upon the petrous portion of the 

 temporal bone, a short distance posterior to the temporal 

 pole, will be seen a depression produced by the eminentia 

 arcuata of the temporal bone. The part of the brain cortex 

 which lies immediately antero-lateral to the depression rests, 

 in the ordinary position, on the tegmen tympani and the 

 petro-squamous suture. It lies, therefore, immediately above 

 the epi-tympanic recess or attic of the tympanic cavity, from 

 which it is separated merely by its membranes and a very 

 thin plate of bone. 



Crossing the medial occipital border, a short distance 

 posterior to the corpus callosum, is the stem or anterior part 

 of the calcarine fissure, already mentioned. It runs forwards 

 for a short distance on the posterior part of the inferior 

 surface. The part of the cortex between it and the splenium 

 of the corpus callosum is the isthmus ; it is continuous, above, 

 with the gyrus cinguli, and, below, with the hippocampal gyrus. 

 The hippocampal gyrus runs forwards and its anterior end 

 turns upwards forming a hook-shaped bend, called the uncus. 

 The posterior part of the hippocampal gyrus is termed the 

 paradentate area (Fig. 156), and the anterior part is known 

 as the piriform area. Continuous with the paradentate 

 area, but lying posterior to it and below the stem of the 

 calcarine fissure, is the lingual gyrus, which runs backwards 

 and turns round the medial occipital border to the medial 

 surface of the occipital lobe, where it was previously noted. 

 Lateral and anterior to the piriform area, and on a lower 

 plane, is a small but definite fissure, called the rhinal 

 fissure, and posterior to the rhinal fissure and lateral to the 

 paradentate area and the lingual gyrus, on a lower plane, is 

 a definite sulcus, which runs antero-posteriorly, and is called 

 the collateral fissure. The gyrus which lies below and lateral 

 to the collateral fissure has been termed the fusiform gyrus ; 

 it- is also called the occipito-temporal gyrus. Between it and 

 the infero-lateral border lies the inferior temporal sulcus, 



