76 
BULLETIN OF THE LABORATORIES 
dense nucleus of paraxial multipolar cells greatly resembling in size 
and form the cells of the third and fourth nuclei. This nucleus is 
situated in the latero-cephalad portion of the thalamus behind the com- 
missure of the hippocampus. It is related to the epiphysis dorsally 
and a strong ventral bundle (taenia thalami) medianly. The whole 
dorso-cephalad part of the thalamus is thickly sown with cells, espe- 
cially medianly, while a dense clustre of cells of the same sort is situ- 
ated near the median line a short distance cephalad of the posterior 
commissure. The axial direction of the last mentioned cells is- verti- 
cal and they give rise to the fibres of Meynerbs bundle. The nucleus 
may be termed nucleus of Meynert’s fasciculus. 
The ascending fascicle of the fornix after meeting the anterior 
commissure passes dorsad to it, entering the septum and becoming 
enveloped in cubical gray masses lying between the corpus callosum 
cephalad and the commissure of the hippocampus caudad. The gray 
mass contains numerous small nuclei. Gradually this mass (and with 
it the fornix fibres) fuse with the hippocampal commissure. 
The strong tract descending from the habenulae passes laterally 
and disappears in the region of the peduncular tracts and can be 
traced no further. 
Comparative data from Didelphys. 
The following memoranda are derived from a series of sections 
from the opossum. Two principal bundles emerge from near the 
ventral surface of the medulla, anteriorly. The median pair bound 
the trigonum and are laterad to the small oculomotor nerve roots. 
These ventral pyramids of the peduncles pass obliquely cephalad and 
laterad to a point caudad to the chiasm, where they turn abruptly 
dorsad. 
The laterad pair of bundles pass obliquely dorsad from the latero- 
cephalad aspect of the medulla to the caudad aspect of the mesen- 
cephalon. 
The second or sensory bundle continues in its dorsal course as a semi- 
circular, and finally a circular bundle, to the horizontal plane including 
the summit of the anterior commissure ; there it begins to break up 
until, at the level of the corpus callosum and hippocampal commissure, 
it becomes a reticular formation beneath the testes. The further course 
of these fibres is obscure, but it appears that they are continued ceph- 
adal through the thalamus and take part in the decussation of the an- 
