THE BASE OF THE FORE-BRAIN. 79 



bundle) turns down into the intermediate stria of the opposite 

 olfactory tract, and the other (the decussating bundle) runs back- 

 ward and outward toward the uncinate region of the limbic lobe. 



The Olfactory Triangle and the Parolfactory Area (of Broca). 

 The triangular portion of the cortex between the medial and 

 lateral olfactory striae, called the triangle (trigonum olfactorium) 

 is continuous medially with the area paroljactoria. The medial 

 stria marks the boundary between them (Figs. 26 and 27). Both 

 are bounded behind by the sulcus par ol) actor ius posterior (trans- 

 verse part), and the oblique part of the same fissure separates the 

 parolfactory area from the gyms subcallosus (peduncle of the 

 corpus callosum). The area parolfactoria (Brocae) is limited 

 in front by a slight curved depression, the sulcus parolfactorius 

 anterior. On the medial surface, this area joins the gyrus cinguli. 



The anterior perforated substance (substantia perforata anterior} 

 of the pars posterior rhinencephali requires further mention (Fig. 

 26). It is separated from the triangle by a very fault groove, 

 the posterior sulcus parolfactorius. Medially, it is in direct con- 

 tinuity with the tuber cinereum. The optic tract bounds it, 

 postero-medially. Laterally, it forms the limen insults in the 

 floor of the fossa cerebri lateralis, where it is overlapped by 

 the temporal lobe. Superiorly, it is continuous with the base 

 of the corpus striatum. Coursing along the inner and outer 

 border of the anterior perforated substance are, respectively, the 

 gyrus subcallosus and lateral olfactory stria, which converge and 

 meet in the hippocampal gyrus. The perforations of this area 

 are for the antero-lateral ganglionic arteries. 



Tentorial Area of the Basal Surface (Figs. 26, 24 and 28). 

 From the temporal pole backward, the basal surface of the cere- 

 bral hemisphere presents three nearly parallel gyri, viz., the 

 inferior temporal gyrus, which forms the infero-lateral border; 

 the fusiform gyrus, the middle one, and the gyrus hippocampi 

 which lies next the mid-brain. The last belongs to the gyrus 

 fornicatus of the limbic lobe; it is continuous, posteriorly, with 

 the lingual gyrus, which forms a part of the medial occipital 

 border of the cerebral hemisphere. The fusiform and inferior 

 temporal gyri belong to the inferior surface of the temporal and 



