374 THE DEVELOPMENT OF CERTAIN FEAi JRES 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 F. 



