OF DENISON UNIVERSITY. 
37 
internal laminated layer of Deiter’s cells dorsad of the ventricle (Plate 
II, Fig. 4, rxl.) These soon form a strong band which swings laterad 
and finally ventrad of the ventricle, as it passes caudad (Plate II, Figs. 
5 and 6.) As the olfactory crus begins to fuse with the hemisphere, 
the superficial olfactory tract takes a position on the ventral surface 'of 
the latter, at the same time dividing into two fasciculi. A small me- 
dian bundle, radix mesialis, (Plate II, Fig. 6, rxm ; see also Plate I, 
Fig. i) can be traced on the ventro-median surface of the hemisphere 
as far back as the cephalic end of the callosum. From both transverse 
and perpendicular longitudinal sections it appears as if its fibres pass 
dorso-caudad from this point into the septum lucidum, entering it from 
below between the cephalic terminus of the callosum and the anterior 
commissure. The fibres, however, have not in any case been actually 
traced through the whole of this course. Even if this be not the true 
course of these fibres, it seems hardly possible that the same relation 
could here prevail as in the opossum, where this radix passes directly 
through the brain cortex up to the gyrus fornicatus. The larger bun- 
dle radix lateralis, passes laterad and caudad toward the pyriform. As 
it passes into this lobe, it loses its compact form and spreads out over 
its ventral surface. It can be traced nearly to the caudal end of the 
pyriform. The inference is that these fibres dip into the pyriform 
along its whole ventral surface, especially toward the cephalic end, 
though this has not been actually observed. 
Returning to the olfactory crus, a section taken through its middle 
portion shows the following structures (Plate II, Fig. 5.) The struc- 
ture of the median half is the same as that of the olfactory bulb. The 
lateral surface is covered with the superficial olfactory tract rxl and 
remains of the glomerular layer. Entad of this tract is a cortical struc- 
ture, c, like that of the hemisphere of which it is really a part. Still 
further entad, adjacent to the ventricle, are fasciculi of the prsecom- 
missural tract of the olfactory crus, pc. That this cortex is not only 
similar to but identical with that of the hemisphere is shown by sec- 
tions taken at the point of union of the olfactory crus with the hemi- 
sphere (Plate II, Fig. 6,) where its continuity is demonstrated. At 
this point it makes up the body of the crus. Passing outward (cepha- 
lad,) it is gradually displaced by the various layers of the olfactory 
bulb, crowded to the dorsal surface, and finally in the bulb itself dis- 
appears entirely. The internal, or praecommissural olfactory tract lies 
within this mass of cortical cells, and I have not been able to trace its 
