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 cms 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 precom- 

 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 err, 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 precommissural olfactory tract lies 

 within this mass of cortical cells, and I have not been able to trace its 



