212 RALPH EDWARD SHELDON 
to continue in the tractus olfacto-thalamicus medialis. Such a 
condition is deceptive, however, as no such fibers could be demon- 
strated in Golgi or Ramon y Cajal preparations. It is evident 
that the Weigert preparations, which fail to show the fine fibers 
as they approach their termination, are, therefore, unreliable in 
a study of the origin and termination of tracts, or the relations of 
two closely associated bundles. 
(3) Nervus terminalis. Earlier agroup of ganglion cells belong- 
ing to the nervus teminalis was described. As shown in fig. 
124 the neurites of these cells pass mesad, lying for a distance 
between the two bundles of the olfactory nerve, along the mesal 
surface of the bulb. This has been demonstrated in Golgi prep- 
arations. In Weigert and vom Rath preparations, an unmedul- 
lated tract, undoubtedly formed by the central processes of these 
ganglion cells, extends from the same region to the hemispheres 
(Sheldon, ’09, Sheldon and Brookover, ’09). Rostrally this 
tract hes embedded in the tractus olfactorius medialis, pars medi- 
alis (fig. 6), on the medial aspect of the bulb. As it passes caudad 
throughout the crus, it still holds approximately the same position 
with reference to the tractus olfactorius medialis, pars medialis 
(figs. 22, 23). When the rostral part of the basal lobe is reached, 
the nervus terminalis gradually turns dorso-laterad through the 
tractus olfactorius medialis to lie between that and the tractus 
olfactorius ascendens (fig. 24). As the anterior commissure is 
reached, the unmedullated fibers separate from their companion 
tracts and decussate in the rostral part of the commissure, end- 
ing in the rostral portion of the pars commissuralis of the corpus 
precommissurale, as described for the nervus terminalis of sela- 
chians by Locy, and in Amphibia by Herrick (figs. 35, 136). 
(4) Distribution of secondary olfactory fibers in the forebrain. 
It will have been noted that secondary olfactory fibers end in a 
very large part of the basal lobes. Fibers of the lateral olfactory 
tract end throughout the lateral, dorsal and latero-ventral por- 
tions of the basal lobes from the rostral end to the lobus pyri- 
formis and nucleus teniae of the,polus posterior. These fibers 
extend, also, into a large part of the central area formerly called 
striatum. The mesal tract, the tractus medialis, carries centri- 
