So BULLETIN OF THE LABORATORIES 



conse^iuence 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. e., 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 comi)act. 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.) 



