8 o 
BULLETIN OF THE LABORATORIES 
consequence has been rolled into a band with a semicircular section, 
so that a section further back (Plate IV, Fig. 2,) reveals the fornix 
fibres dorsally attached to the hippocampus. This throws needed 
light upon the fornix, hippocampus, and their relations. The hippo- 
campus is essentially the whole caudad margin of the cortex which by 
continued peripheral increase has rolled itself in the longitudinal di- 
rection and at the same time arched about the peduncles as they con- 
verge from the striatum toward the sides of the thalamus. This pass- 
age of the peduncular fibres can be well seen in sections somewhat 
cephalad to Fig. i, Plate V, and in Plate V, Fig. 2, where the pedun- 
cular fibres have already crossed and lie mesiad from the optic tract 
which forms the lateral wall of the thalamus. Near the lower ventral 
and median extremity one may detect the remnant of the fornix tract 
on its way to the mammillary body. Laterally, the ragged portion of 
gray matter projecting into the ventricle is the remnant of the striatum 
after the crossing of the fibres to the thalamus. ' 
Returning to the hippocampus, its fibres pursue as nearly as pos- 
sible the usual course, i. <?. , part pass directly across, forming the com- 
missural part of the fornix, and other fibres descend in the body of 
the fornix to the body of the thalamus and thence to appropriate nu- 
clei in that organ. 
In the region of the anterior commissure, a number of the ventral 
bundles of fibres, which may be regarded with a high degree of proba- 
bility as sensory in function, now begin to cross to the thalamus, mean- 
while the dorsal bundles which occupy the striatum proper become 
constantly more compact. The principal sensory bundles seem to be 
driven medianly until the sides of the thalamus are occupied by a 
rather compact motor column. The relations described are well shown 
in Figs. I and 2, of Plate V. Fig. 2 also shows the fornix fibres near 
the mammillary body. 
The olfactory tracts are somewhat difficult to follow. Two of 
them are distinct and may be traced to the same general region of the 
hemispheres and thalamus. The inner tract passes directly backward 
from the centre of the crus olfactorius (Plate II, Fig. i,) to beyond 
the anterior cornu of the ventricle, where it seems to divide, sending 
a branch to the superficial tract. Thence it may be traced backward 
in successive transverse sections to the region of the anterior commis- 
sure. (In Fig. 8 , Plate I, the olfactory tract lies a little above and to 
the left of the point indicated by c.) 
