412 J. B. JOHNSTON 
The whole of this ring receives fibers from either the lateral or 
medial olfactory tract. This continuous complex of small- 
celled nuclei seems to serve as an intermediate selecting and 
distributing station through which olfactory impulses are for- 
warded to the cortical eenter for sensation, the hippocampus; 
or to one of the motor correlation centers in the diencephalon, 
or to centers lower down the brain stem (compare Johnston ’15 a). 
The greater part of the pyriform lobe made up of large cells is 
probably concerned with olfacto-somatic correlation. Other 
places for correlation of olfactory and somatic impressions are 
probably found in the amygdaloid complex and in the hippo- 
campus (subiculum). The distribution of large cells in the 
pyriform lobe probably gains significance from their relation to 
the pallial thickening. 
The boundary line between the pyriform lobe and the general 
pallium is less distinct in the caudal part than elsewhere. As 
the pyriform lobe is followed caudad in sections to the point 
where it forms the whole thickness of a part of the wall of the 
ventricle (figs. 13 to 15) the cell-free zone at first continues as a 
very clear oblique dividing line in this wall (fig. 14). This over- 
lapping of the general pallium by the border of the pyriform lobe 
is very characteristic. This dorsal border of the lobe rises dorsally 
in its caudal portion as the model clearly shows (fig. 5). In 
transverse sections through the region in which the small-celled 
portion of the pyriform lobe spreads ventrad to merge with the 
nucleus of the lateral olfactory tract, the cell masses of the 
dorsal ventricular ridge begin to be connected by a thick curved 
layer of cells with what appears to be the cell layer of the pyri- 
form lobe in the lateral wall (fig. 15). When this relation is 
studied in sections farther caudad (figs. 11, 12) it is clearly seen 
that it is the general pallium which thus enters into continuity 
with the ventricular ridge. In transverse sections there is no 
sharp boundary between pyriform lobe and general pallium. 
It is noticed, however, that there is a narrow portion of the wall 
adjacent to the dorsal boundary of the lobe in which the cells 
are placed close to the ventricular surface (fig. 12). The oblique 
line bounding the lobe dorsally at length gives way to a narrow 
