File:Page 135 of "Brain and spinal cord; a manual for the study of the morphology and fibre-tracts of the central nervous system.jpg

English: Text Appearing Before Image: while within the third layer are found larger pyramidal cells with very long primordial branches ; moreover, of these cells the largest are very deeply placed, whereby the conspicuous radial striation, the stratum radiatum, is produced. The layer of polymorphic cells contains almost exclusively small irregular cells, that are embedded within a close network of nerve-fibres. Hippocampus and Gyrus Dentatus.The hippocampus, or cornu Ammonis, and the gyrus dentatus represent two spe-cial convolutions. On following the gyrus hippocampi dorsally, one reaches the subiculum, that constitutes that part of the hippocampal convolution in which gradually begins a change in the structure of the cerebral cortex, leading finally to the typicalstructure of the hippocampus. The white substance splits into two layers : the onepasses to the free surface of the hippocampus and constitutes the alveus, the other passesto the lateral wall and roof of the inferior horn of the lateral ventricle. The alveus is

Text Appearing After Image:

Layer ofpolymorphic cells Layer ofpyramidal cells ^loleddar layer Fig. 117.—Hippocampus or cornu Ammonis and gyrus dentatus in transverse section. Schematic, THE HIPPOCAMPUS, 121 continuous with the fimbria. The uppermost layer of the gray substance, the substantiareticularis alba, corresponding to the molecular layer of the typical cortex, divides intoa superficial and a deep stratum. The superficial layer adjoins the molecular layer of thegyrus dentatus and forms the lamina medullaris circumvoluta. The deep layer forms thestratum, lacunosum, that arches around and embraces the lamina medullaris and ends in arecurved hook at the medial side of the cell-layer of the gyrus dentatus. Between thelamina medullaris circumvoluta and the stratum lacunosum, lies the stratum moleadare.The pyramidal cells of the subinculum gradually collect into a single layer of cells as theyapproach the hippocampus. At first the arrangement of the cells is still irregular, towardsthe gyrus dentatus the cell