232 RALPH EDWARD SHELDON 
Descending pathways 
Nervus terminalis. In this case an impulse may travel from 
the periphery to ganglion cells situated among the olfactory nerve 
fibers and thence to a decussation among the rostral cells of the 
bed of the anterior commissure. Its further course is not known. 
The olfactory neurones of the first order end throughout the 
lateral, rostral and rostro-medial face of the bulb. Fibers from 
all three areas form the tractus olfactorii lateralis, and medialis, 
pars lateralis, for the nucleus olfactorius lateralis and nucleus 
pyriformis of the basal lobes (fig. 137). From the lobus pyri- 
formis originate the tractus teniae for the habenula of the opposite 
side, and the tractus olfacto-hypothalamicus lateralis for the 
nucleus cerebellaris hypothalami and the nucleus diffusus lobi 
lateralis of the same side (fig. 137). 
The corpus precommissurale stands in relation, chiefly, with 
the more medial portion of the bulb, through the tractus olfacto- 
rius, pars medialis and pars lateralis, which terminate largely in 
the nucleus medianus of the same and opposite side, in the com- 
missure bed, and in the pars supracommissuralis of the same side. 
The pars lateralis, after decussation, sends also a few fibers to the 
nucleus intermedius (fig. 137). 
From the corpus precommissurale there are, likewise, two great 
pathways open. In one case cells with short neurites, forming 
the fibrae precommissurales striatici, transfer the impulse to 
the palaeostriatum, whence it is carried by the tractus strio- 
thalamicus to the nuclei anterior tuberis, prerotundus, rotundus, 
subrotundus, posterior thalami, cerebellaris hypothalami and dif- 
fusus lobi lateralis of the same side; and the nuclei rotundus, 
subrotundus, and diffusus lobi lateralis of the opposite side (fig. 
139). The other connection is through the median forebrain 
bundle, which places the nucleus supracommissuralis chiefly, 
but other parts of the corpus precommissurale as well, in relation 
with the nuclei rotundus, subrotundus and posterior thalami. 
A third connection, less prominent but of considerable morpho- 
logical importance, is with the nucleus preopticus. This receives 
twosmall bundlesfrom the nucleus medianus, the tractus mediano- 
