25 26 
Fig. 23 Section through the pallial thickening in front of the ventricular 
ridge. In this and the next three figures the pyriform lobe is bulged out by the 
pallial thickening. Although the lentiform nucleus still meets the ventricle, 
the caudate is greatly enlarged. From here forward the hippocampus is scarcely 
if at all recognizable. The subiculum continues between the general pallium and 
the hippocampal primordium. The dividing line between primordium hippo- 
campi and parolfactory area is again clear. In this section the ventral ventric- 
ular groove reaches its greatest depth and width. Forward from this the 
thickening of caudate, parolfactory nucleus and tuberculum nearly obliterate it. 
Fig. 24 Section through the middle of the pallial thickening. Islands of 
Calleja begin to appear in the medial wall. The lentiform nucleus is pushed 
toward the surface by the caudate. For a detail of the pyriform lobe and part 
of the pallial thickening compare figure 40. 
Fig. 25 Section through the caudal part of the tuberculum olfactorium and 
the head of the caudate. Note the high dorsal prominence caused by the pallial 
thickening. This scarcely shows satisfactorily in the figures of the whole brain 
or model. <A part of the apparent thickness of the cell layer is due to the section 
being slightly oblique to the curvature of the dorsal pallium but the appearance 
of a distinct peripheral layer of cells is not due to this. Islands of Calleja are 
grouped in the medio-basal angle. Dark masses farther laterad are merely 
clumps of large cells in the lentiform nucleus. 
446 
