THE TEMPORAL LOBE 



855 



occasionally interrupted by a few weak twigs of the lateral fissure. It is separated 

 from the gyrus below by the superior temporal sulcus, which is parallel with the 

 posterior ramus of the lateral fissure and is frequently called the parallel sulcus. 

 The posterior extremity of this sulcus divides the angular gyrus of the parietal 

 lobe, and its anterior end disappears in the temporal pole, sometimes as a continu- 

 ous groove, sometimes in isolated pieces. 



The middle temporal gyrus likewise begins in the temporal pole and is con- 

 tinuous backward into the angular gyrus of the parietal lobe. 



The inferior temporal gyrus forms the infero-lateral border of the temporal 

 lobe, and is usually more broken up than the two gyri above it. It begins 

 continuous with them in the frontal pole, and extends horizontally backward into 

 the lateral gyri of the occipital lobe. It is separated from the middle gyrus by the 

 middle temporal sulcus, which likewise is never so continuous a furrow as the 

 superior temporal sulcus. Frequently this sulcus occurs in detached portions 

 and often terminates within the temporal lobe. 



Fig. 674. — Outline Drawing op Convex Surface of Left Cerebral Hemisphere. 



(After Toldt, "Atlas of Human Anatomy," Rebman, London and New York.) 



Precentral sulcus Central sulcus (Rolandi) 



Inferior 

 frontal sulcus\ 



Superior 

 frontal sulcus 



Horizontal ramus 

 of interparietal 

 sulcus 



Transverse 

 occipital 

 sulcus 



Inferior 

 frontal 

 gyrus 



Orbital portion 



Triangular portion \ 



Opercular portion " 



Operculum 



The fusiform gyrus is in the basal and tentorial surface of the temporal lobe 

 (fig. 676). Its usual somewhat spindle shape suggests its name, and it is con- 

 tinuous backward into the occipital gyri, or its posterior end may be completely 

 isolated by a union of the inferior temporal sulcus and the collateral fissure, 

 which two furrows separate it from its neighbours on either side. Anteriorly the 

 fusiform gyrus runs into the common substance of the other three gyri at the 

 temporal pole. 



The lingual gyrus is usually included in the tentorial surface of the temporal 

 lobe, though in some texts it is regarded as a part of the occipital lobe. Its larger, 

 posterior portion lies within the boundaries of the occipital lobe. Bounded 

 laterally by the collateral fissure, it is continuous anteriorly into the hippocampal 

 g>^rus of the rhinencephalon (fig. 676). 



All of the sulci give off occasional lateral twigs (transverse temporal sulci) which 

 themselves may or may not branch, and which tend to divide the main gyri into 

 transverse temporal gyri. 



The lateral fissure (fissure of Sylvius). — As promised in its origin by the over- 

 lapping and enclosing of the broad fioor of the Sylvian fossa by the adjacent folds 

 of the pallium, the lateral fissure is the deepest and most conspicuous fissure of 

 the cerebral hemisphere. Its main divisions are a short stem and three main 

 branches. The stem lies in the basal surface of the hemisphere, where it begins 



