OF DENISON UNIVERSITY. 
33 
Reference to Plate III will render these statements of Stieda clear 
in spite of the condensed form in which they are necessarily presented. 
The first fold mentioned by him, the primary fold of the hippocampus 
(Plate III, a,) does not appear in transverse sections to be a mere fold, 
or fissure, springing from behind ; but it is complicated by the fact 
that its dorsal portion is pushed much farther cephalad than its ven- 
tral. The latter only passes as far as the level of the corpus mam- 
millare (Figs. 3 and 4.) Cephalad of this region the lamina next the 
the lateral ventricle, which I have called lamina ectalis (the superior 
lamina of Stieda, Fig. 3, k,) is in direct continuity ventrally with the 
other, the lamina entalis (or lamina inferior of Stieda, Fig. 3, //.) The 
fact that the dorsal portion of the primary fold of the hippocampus 
appears in transverse sections to pass much farther cephalad than the 
ventral portion is due to the arched form of the hippocampus itself. 
By reason of this forward arch the caudal portion of the hippocampus 
appears in longitundinal section, the cephalic portion in transverse 
section in these figures. The laminae ectalis and entalis together con- 
stitute the gyrus fornicatus. By means of this primary fold the hippo- 
campus is pushed far cephalad under the callosum beyond the chiasm 
until it comes into direct continuity with the fornix body in the region 
of the lamina terminalis. The primary fold reaches almost to the end 
of the gyrus fornicatus, but in Fig. i has disappeared. 
The true relations of the gyrus uncinatus are much more diffi- 
cult to make out. It is formed, as Stieda says, by a secondary fold of 
the gyrus fornicatus ; but it is not, like the primary fold, due to an in- 
vagination, or convolution. It is rather a reflected portion of the 
margin of the lamina entalis. This margin is folded back upon itself, 
the folded portion, i. e. the gyrus uncinatus, being refiexed ventrad 
and cephalad, so that the free margin of the latter lies next to the 
diencephalon and mesencephalon. The convexity of the fold is di- 
rected cephalad, and toward the caudal end of the hippocampus it 
apparently in transverse sections increases greatly in size. This ap- 
pearance, however, is due to the arched character of the hippocampus 
by which the caudal portion is seen in longitudinal section, as above 
alluded to. That the gyrus uncinatus is a true fold from the gyrus 
fornicatus is not very obvious from these sections, since the gray mat- 
ter of the two gyri is nowhere in direct continuity. Moreover the cell 
structure is essentially different, the gyrus fornicatus having typical 
flask-cells, but the gyrus uncinatus snialler deeply staining cells which 
