412 THE BRAIN 



Sulcus Tempuralis Medius. The middle temporal sulcus, 

 which lies between the middle and the inferior temporal gyri, 

 is very irregular in its mode of formation ; not infrequently it 

 is represented by two or more separate portions. 



The Gyri of the Lateral Surface of the Temporal Lobe. 

 There are three gyri on the lateral surface of the temporal 

 lobe superior, middle, and inferior. 



Gyrus Temporalis Inferior. The inferior temporal gyrus 

 lies below the middle temporal sulcus ; it forms the temporal 

 part of the infero-lateral border of the hemisphere, and will 

 be seen again on the inferior surface of the temporal lobe, 

 where it is separated from the fusiform gyrus by the inferior 

 temporal sulcus. 



Gyrus Temporalis Medius. The middle temporal gyrus 

 lies between the middle and the superior temporal sulci, and 

 it is more or less continuous, posteriorly, with the angular and 

 the post-parietal gyri. 



Gyrus Temporalis Superior. The superior temporal gyrus 

 lies between the superior temporal sulcus and the posterior 

 ramus of the lateral fissure, and it extends forwards to the tip 

 of the temporal pole of the hemisphere (Fig. 152). 



The Upper Part of the Temporal Lobe^ which forms the 

 lower wall of the posterior ramus of the lateral fissure, is in 

 relation with the insula and the lower parts of the parietal 

 and frontal lobes. The dissector can display it by gently 

 separating the lips of the fissure, and upon it two gyri, running 

 backwards and medially, will be seen ; they are the anterior 

 transverse temporal gyms (Heschl's convolution) and the 

 posterior transverse temporal gyrus. The anterior transverse 

 temporal gyrus and the portion of the posterior part of the 

 superior temporal gyrus adjacent to its lateral end constitute 

 the acoustic area of the brain cortex (Fig. 153). 



The Inferior Surface of the Temporal Lobe forms the 

 greater part of the posterior portion of the inferior surface of 

 the hemisphere, and in brains hardened in situ it is marked, 

 anteriorly, by an obvious depression due to the eminentia 

 arcuata of the anterior surface of the petrous part of the 

 temporal bone. 



The Fissures and Sulci of the Inferior Surface of the 

 Temporal Lobe are : (i) part of the chorioidal fissure (Fig. 138); 

 (2) the collateral fissure ; (3) the stem of the calcarine fissure ; 

 (4) the rhinal fissure; and (5) the inferior temporal sulcus. 



