. Carnegie Institution of Washington publication. 374 THE DEVELOPMENT OF CERTAIN FEAiJRES OF THE CEREBELLUM. cells, constitutes a depot for reinforcement of other layers, or disappears in part. The most general view is that of Cajal, that the disappearance of the outer nuclear layer represents merely a change of position. In the human brain these cells are disappearing at a time when, as is easily seen in figures 5 and 6, the increase in cerebellar surface is very great. The number of cells in the outer nuclear layer, seen in figure 1, is very striking; but when we com- pare figure 4 (a cross-
. Carnegie Institution of Washington publication. 374 THE DEVELOPMENT OF CERTAIN FEAiJRES OF THE CEREBELLUM. cells, constitutes a depot for reinforcement of other layers, or disappears in part. The most general view is that of Cajal, that the disappearance of the outer nuclear layer represents merely a change of position. In the human brain these cells are disappearing at a time when, as is easily seen in figures 5 and 6, the increase in cerebellar surface is very great. The number of cells in the outer nuclear layer, seen in figure 1, is very striking; but when we com- pare figure 4 (a cross-section of the cerebellum of a 6-months fetus from the cortex. FIG. 6.—Contour drawing of one-half of the cerebellum of a child 2 years of age. of which figure 1 is taken) with figure 5, it is evident that we have at 16 days a surface at least 10 times that of the 6-months fetus. This means that this outer nuclear layer would furnish to the nuclear layer proper, as present in the child of 16 days, one layer of cells with as much space between adjacent cells as is found between alternate cells in the outer nuclear layer of the 6-months fetus. Physically, the absorption of the outer by the inner nuclear layer is very easy, and it would seem unnecessary to postulate the total disappearance of any of these cells. THICKNESS OF MEDULLA AND CORTEX. If, in our study of the growth of the cortex, we make a comparison of the thickness of the medullary and cortical portions of the cerebellum, we ascertain that a relation of about 1:1 is maintained, as shown in table Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original Carnegie Institution of Washington. Washington, Carnegie Institution of Washington
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