THE DEVELOPMENT OF THE CEREBRAL CORTEX 



E. LINDON MELLUS 

 From the Anatomical Laboratory of the Johns Hopkins University 



TWO FIGURES 



During the course of an investigation (still incomplete) of the 

 so-called 'motor area' in man (anterior central convolution of the 

 cerebral cortex) I had occasion to examine sections from that 

 area in the brain of an eight months foetus. To my surprise I 

 found the corona radiata of both central convolutions thickly 

 sown with what appeared to be migrating cells. These cells 

 were in various stages of development, the large majority resem- 

 bling the n^roblasts just leaving the matrix in earlier stages, but 

 many were well advanced in development, the nucleus having a 

 distinct nucleolus and being enveloped by a considerable cell 

 body. This cell body was either round or ovoid. Many of the lat- 

 ter form had a distinct apical process at one or the other extrem- 

 ity, this being sometimes directed toward the cortex, at other 

 times away from it as if the nucleus were being propelled so rapidly 

 that the enveloping protoplasm was inclined to drag behind. 

 The long diameter of the ovoid cells seemed always to indicate 

 the direction of the movement, some of those quite near the 

 cortex of the fissure walls having apparently turned toward the 

 cortex and in such the long diameter was at an acute or almost 

 right angle to that of those more toward the center of the corona 

 radiata. The granules or undeveloped nuclei scattered through 

 the corona radiata were of two sorts and sizes. The smaller about 

 5 micra in diameter stained deeply and showed no nucleolus, the 

 others about 10 micra in diameter were faintly stained and con- 

 tained two or more dark spots. At first I was inclined to look 

 upon the smaller of these two granules as spongioblasts and the 

 paler as neuroblasts, but I found as many of the latter as the 

 former in the first (molecular) layer of the cortex. In this por- 



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THE AMERICAN JOURNAL OF ANATOMY. VOL. 14, NO. 1 



