OF DENISON UNIVERSITY. 
79 
position, and the superficial one spreads over the whole pyriform lobe. 
The next section (Fig. 8, Plate II,) taken behind the chiasm shows 
the optic tracts collected on either side of the now distinct thalamus and 
separated by the infundibulum. The olfactory tract crosses the nar- 
row third ventricle by a sudden curvature via the anterior commissure 
which seems to be a genuine commissure of the olfactory and adjacent 
sensory tracts. 
An important tract now first appears. It consists of fibres passing 
obliquely dorsad behind and ventrad to the commissure. Neither 
upper nor ventral terminus appears in this section, but the fibres can 
be traced ventro-laterad and caudad to form the descending tracts of 
the fornix, as already seen in longitudinal sections, and cephalad and 
dorsad until they unite the so called fornix nuclei of both sides by a 
strong decussational band near the ventro-caudad border of the cal- 
losum. We can not determine whether there is absolute continuity be- 
tween all these fibres and the commissure of the hippocampus. The 
latter is certainly chiefly made up of the fibres from the fornix, but it 
also appears that some of the fibres from the hippocampus are truly 
commissural while, on the other hand, some at least of the fornix fibres 
appear to terminate in the gray matter of the fornix nucleus or body. 
The farther course of the descending tract of the fornix has been 
given above. We do not find evidence of the absolute continuity of 
the fibres of this tract with those of the fasciculus of Vicq d’Azyr or 
ascending fornix tract of Ferrier. 
The body or nucleus of the fornix adheres to the inferior surface 
of the corpus callosum, but there is no evidence of organic connection. 
Plate ,1, Fig. 8, illustrates a section near the front of the corpus 
callosum. The fornix body has already become distinct from the 
corpus striatum. The central tract of the olfactory nerve lies ventrad 
and slightly dorsad from the line e, the external tract being near b. 
Plate II, Fig. 8, represents a section at the anterior commissure. 
The prominences of the fornix body are here quadrangular and medi- 
anly give rise to tracts which pass caudad to the commissure. The 
optic tract appears near the median line above i. Plate IV, Fig. i, 
exhibits the relations of the tracts descending from the fornix nucleus. 
In sections immediately following, a very broad band of fibres con- 
nects these two prominences and their extension also unites the ventral 
surfaces of the hippocampus. This belt of fibres has suffered the 
same involution that the substance of the hippocampus has, and in 
