194 RALPH EDWARD SHELDON 
48, 49, 56). The primordium hippocampi receives secondary 
olfactory fibers from the tractus olfactorius medialis and a few 
commissural fibers associated with the commissura corporium 
precommissuralium. The neurites of its cells descend partly 
with the tractus strio-thalamicus and partly with the tractus 
olfacto-thalamicus medialis, pars dorsalis. No tertiary olfactory 
fibers could be traced, in Golgi preparations, either from the 
lobus pyriformis or the corpus precommissurale to the primordium 
hippocampi. In Ramén y Cajal preparations, however, mingled 
with the fibers of the commissura corporium precommissuralium 
rostrally are a number of unmedullated fibers connecting the 
nucleus medianus with the primiordium hippocampi. From the 
conditions in amphibians, reptiles and mammalsit seems extremely 
probable that these represent the tractus area-hippocampalis rectus 
of Kappers and constitute an association path between the pre- . 
commissural body and the primordium hippocampi. The mor- 
phology of this region will be considered more in detail further on. 
(ec) Nucleus olfactoriuslateralis. Laterally, extending from the 
extreme rostral end of each basal lobe to the extremity of the 
polus posterior, lies the lateral olfactory area; the area olfactoria 
of Edinger, the lobus olfactorius posterior, pars lateralis of Gold- 
stein, area olfactoria posterior lateralis of Kappers (’06), area 
olfactoria lateralis of Kappers and Theunssen (’08). The nucleus 
olfactorius lateralis is here divided into itwo parts, both rostral 
to the sulcus ypsiliformis, and consisting of rather evenly dis- 
tributed, somewhat scattered cells. The more rostral appears 
externally as the tuberculum anterius (figs. 2 and 3), while the 
more caudal presents superficially the tuberculum laterale. The 
nucleus olfactorius lateralis covers as a cap the entire rostro- 
lateral surface of each basal lobe. At the extreme rostral pole it 
is restricted to the lateral aspect but passing caudally it gradually 
spreads dorsally covering the dorso-lateral aspect of each lobe, at 
the level of the sulcus ypsiliformis (figs. 25, 38). 
The lobus pyriformis, so named since it is closely related to the 
pyriform lobe of mammals, consists dorsally and caudally, of 
evenly distributed scattered cells very similar to those of the nu- 
cleus olfactorius lateralis (figs. 38, 56, 66,67). Ventrally, imme- 
