OF DENISON UNIVERSITY. 
85 
with the roof of the thalamus. The splenialis fissure grows deeper 
and curves ventrad, finally curving ventro-mesad (Plate A, Fig. 5.). 
Meanwhile, the medullary fibres of both the fornicate and uncinate 
gyrus accumulate to produce the cephalad parts of the fornix. The 
relations remain nearly the same throughout the posterior parts of the 
cerebrum though the curvature of the hippocampus about the thalamus 
causes the transverse sections to fall in other planes. The longitudin- 
al sections of Plate B show that the relations between the two gyri are 
maintained to the very subiculum. 
The cellular structure of the hippocampus bears out the distinc- 
tions already made. The cells in both are densely clustered and form 
practically but a single series. The peripheral processes are from the 
apices of the elongate fusiform or spuriously pyramidal cells. The 
entad extremity is frequently almost equally prolonged. The nuclei 
are large and clear. The cells of the fornicate gyrus are nearly twice 
as large as those of the uncinate and the latter also lie in a different 
plane, a fact due to the faulting or rotation of the gyrus as a whole. 
The structure of the hippocampus and its great complexity in other 
mammals is due chiefly to the flexture and caudad thrust of the 
callosum. 
For a very complete historical account of the hippocampus and 
related structures see the works of Honegger ^ while the most recent 
work on the histology is that by Sala.^ 
After the painful attempt of Honegger to bring into harmony the 
infinitely diverse nomenclature of this subject we can but feel that a 
strict morphological terminology best meets the case. Embryology 
and comparative anatomy leave no doubt that we are dealing with two 
folds of the caudo-mesal cortex which are simply plicated and then 
curved upon each other. One margin of the structure is connected 
directly with the occipital cortex, the other with the tela and proplex- 
us. The mesal convolution is the fascia dentata or gyrus uncinatus 
produced, the lateral convolution is the gyrus fornicatus. The alveus 
is the ental fibre zone of the gyrus fornicatus and the fimbria is the 
transition of the alveus into the fornix and hippocampal commissure. 
1 J. Honegger. Vergleichend-anatomische Untersuchung ueber den Fornix 
und die zu ihm in bezieliung gebrachten Gebilde im Gehirn des Men- 
schen und der Sangetbiere. Genf. 1890. 
2 L. Sala. Zur feineren Anatomie des grossen Seepferdefusses. Zeiischrift 
fue wissenschaftliche Zoologie, LI I. I. 1891. 
