108 LABORATORY OUTLINE OF NEUROLOGY 



126. Cortical olfactory tracts. All parts of the olfactory area 

 discharge tracts of the third order into the cerebral cortex 

 (hippocampus and gyrus hippocampi). 



(1) Tractus olfacto-corticalis medialis. These fibers ascend 

 from the medial and intermediate olfactory areas close to the 

 median plane between the corpus callosum and the anterior 

 commissure to enter the body of the fornix and fimbria. They 

 are drawn, but not named, in the region marked S in Fig. 106 of 

 Herrick ('18). They pass through the fimbria to terminate in 

 the hippocampus (see Section 127). 



(2) Stria longitudinalis medi alis (" nerve" of Lancisius). A 

 few fibers belonging to the same system as the last pass dorsally 

 instead of ventrally of the corpus callosum. By exposing the 

 dorsal surface of the callosum they can be seen curving around 

 the genu, passing backward along its dorsal surface close to the 

 median plane, then curving ventrally around the splenium to 

 enter the underlying hippocampus (see Burkholder ('12), 

 Plates XI and XII). These fibers are accompanied by the 

 thin gray "indusium verum," which is a vestige of an extension 

 of the hippocampus above the callosum which is found in the 

 lowest mammals. See Herrick ('18), Fig. 106, h. sc., and 

 Johnston ('06), Chap. XVIII. These structures are smaller in 

 man than in the sheep, though they may still be recognized. 

 See Cunningham ('15), Fig. 554, p. 626; Morris ('14), Fig. 672, 

 p. 852; Spalteholz ('09), Fig. 715; Toldt ('04), Fig. 1198, p. 780; 

 Villiger ('12), Figs. 32-34, 36, 39. 



(3) Tractus olfacto-corticalis lateralis. These fibers arise 

 from the lateral olfactory nucleus and enter the ventrolateral 

 end of the hippocampus in the uncus region of the temporal 

 lobe. They accompany those of the lateral olfactory tract. 



The uncus and adjacent parts of the temporal lobe are of 

 transitional type. Forward they merge into the lateral olfac- 

 tory nucleus, laterally into the neopallium (see Section 112) 

 through the gyrus hippocampi, and medially into the archipal- 

 lium through the hippocampus (see Section 127). 



127. The hippocampus and fornix. When the relations of 

 the olfactory tracts of the sheep already described are clearly 

 in mind, remove the septum pellucidum and look into the 

 lateral ventricle, drawing apart the corpus callosum and the 



