Talk:Paper - The embryonic cerebral hemisphere in man (1921)

From Embryology


By MARION HINES, Pu.D., University of Chicago

"Lue medial wall of the cerebral hemisphere of embryos 16 mm. to 30 mm. in length is not perfectly smooth. Its otherwise even contour is broken by a shallow groove, which extends from the olfactory bulb to the tip of the temporal pole. This is the fissura hippocampi, the “ Bogenfurche” of His. The primordial hippocampus can be identified in embryos about 10 mm. in length by a thicker wall, a narrower matrix, and a more clearly defined marginal velum than the area immediately contiguous to it laterally. This region is separated from the area cpithelialis by a sulcus limitans hippocampi.

The fascia dentata arises in the matrix of the ventral limb of the hippocampus as a group of deeply-stained cells, which migrate dorsal-ward into its marginal velum. The telencephalon medium is divided into terminal plate and roof by the angulus terminalis. The area epithelialis contiguous to the midplane-region differentiates into three characteristic areas, the septum ependymale, the area intercalata and the lamina epithelialis; that which lies contiguous to the main body of the lamina terminalis forms the septum.

In embryos of 16 mm. in length the ventro-lateral region of the hemisphere is very thick, containing two slight elevations, the medial and lateral roots of the corpus striatum. At this age the medial hillock is larger than the lateral. But in embryos of 20 mm. they are approximately equal in length and depth; and in those of from 27 mm. to 43 mm. the lateral hillock is the greater.

In early stages the cerebral hemisphere expands by intrinsic growth of cach particular sector and especially by a marked extension of neopallia] tissue. It elongates by acceleration of mid-line growth in the region of the lamina terminalis and the di-telencephalic fold, and by the expansion of areas of new tissue, which form the frontal, parietal and temporal poles. A study of histological differentiation in the early development of the telencephalon in man gives a method of measuring the relative growth of its several parts and thus of contributing to our knowledge of its intrinsic development.