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BULLETIN OF THE LABORATORIES 
the commissure. The cortex is about 2 mm. deep and the white fibre 
layer below is one half as thick. The fibres from any given region 
gradually accumulate in bundles adjacent to the corpus striatum and 
finally perforate it obliquely. Here they pursue an oblique ventral 
course and tend to accumulate in still larger bundles. The larger bun- 
dles are in the dorsal part of the striatum, the whole substance of 
which is filled with small fusiform or flask cells of uniform size and 
irregular direction. The form of the striatum is here irregularly quad- 
rangular. Besides the fibres radiating to the corpus striatum, the white 
matter beneath the cortex contains an approximately equal number, 
which obviously are converging to the corpus callosum. These fibres 
or rather similar fibres from cephalad parts of the hemisphere collect 
above the ventricle (by it separated from the striatum) to form the 
callosal tract, which is separated from the median fissure by a thin 
septum lucidum. The septum is here crowded with fusiform cells 
and is separated from the cortex proper by the calloso-marginal fissure. 
Between the septum and the corpus striatum, ventrad from the callosal 
tract, is a ganglionic mass like the striatum in its cell structure, but 
free from fibre tracts and separated from the septum by a poorly aggre- 
gated tract. This mass is associated with the body of the fornix. 
Below the corpus striatum is the central olfactory tract, which 
consists of two portions, and is very distinct from everything about it. 
The entire ventral portion (or pyriform lobe) is peculiar m the 
absence of any orderly arranged cortical gray. On the other hand, 
its cells are aggregated in small, dense clusters or sinuous masses and 
a little distance within the cortex is a greater number of small, disperse 
fibre tracts which appear to be derived from the superficial olfactory 
tract, which latter here occupies the latero- ventral aspect. 
(VT/, 21.) In sections near the the front of the callosum the 
ventricle has extended ventrally and severed the non-fibrous median 
gray or fornix nucleus, making of it an intraventricular aggregate, the 
medio-ventral part of the septum lucidum remaining distinct from it. 
In sections further caudad the tracts near the ventral surface have re- 
treated dorsad and collected near the olfactory tract. The tract from 
the ventral part of the septum has descended toward the ventral region 
and dense clusters of large fusiform cells gather in its medio-ventral 
portion. 
Gradually the intra-ventricular gray matter (fornix body) assumes 
a quadrate section, the central olfactory tract begins to reach a median 
