78 BULLETIN OF THE LABORATORIES 



the commissure. The cortex is al)out 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 a|)pear to be derived from the superficial olfactory 

 tract, which latter here occupies the latero- ventral aspect. 



(VL/, 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 



