THE BASE OF THE FORE-BRAIN. 8 1 



which represents an important lateral boundary of the rhinen- 

 cephalon in animals with highly developed sense of smell. It 

 indicates in man the boundary between the hippocampal and 

 fusiform gyri. A half inch behind the ectorhinal sulcus is the 

 anterior end of the collateral fissure. 



Fissura Collateralis (Figs. 26 and 28). The collateral fissure 

 extends in a somewhat curved course from near the temporal 

 pole almost to the occipital pole. Its anterior two-thirds separates 

 the hippocampal from the fusiform gyrus; its posterior one- third 

 completes the medial and upper boundary of the fusiform gyrus 

 and separates it from the gyrus lingualis. 



Inferior Temporal Sulcus (Fig. 26). Only one sulcus belongs 

 wholly within the inferior surface of the temporal and occipital 

 lobes. It extends from a point near the occipital pole forward 

 along the infero-lateral border of the hemisphere almost to the 

 temporal pole, and incompletely separates the inferior temporal 

 gyrus and the lateral occipital gyrus from the gyrus fusiformis. 

 Very frequently the sulcus has two or more interruptions. It 

 may be called the temporo-occipital sulcus. 



Gyrus Fusiformis. One gyrus only is found entirely within 

 the inferior temporo-occipital region (Figs. 26 and 29). That 

 is the fusiform (temporo-occipital gyrus). It extends from near 

 the occipital pole forward and forms the temporal pole. The 

 posterior nine-tenths of its medial boundary is formed by the 

 collateral fissure and the anterior one-tenth by an imaginary line 

 and the ectorhinal sulcus; laterally, it is bounded by the inferior 

 temporal sulcus. 



Gyrus Lingualis. The gyrus lingualis lies above and medial 

 to the posterior one-third of the collateral fissure; inferior and 

 lateral from the calcarine fissure. It is continuous with the gyrus 

 hippocampi of the limbic lobe in front. The gyrus lingualis 

 (Fig. 29) forms nearly all of the medial occipital border of the 

 hemisphere. It contains a part of the receptive visual center 

 (Figs. 55 and 57). 



Limbic Lobe (Lobus Limbus), Inferior Part. The gyrus 

 hippocampi of this lobe is visible on the inferior surface of the 

 fore-brain (Fig. 26). Notice how this crescentic gyrus embraces 

 6 



