DEVELOPMENT OF THE CEREBRAL CORTEX 



109 



From the outer edges of this band radially directed streams of 

 nuclei could be followed into the hiatus oj each contiguous con- 

 volution. Sagittal sections through the occipital operculum 

 showed similar conditions, the ventricle surrounded by this broad 

 band of deeply stained nuclei from the external borders of which 

 streams of cells radiated toward the surrounding cortex. 





Fig. 1 Transverse section of occipital lobe of the brain of an eight-months 

 human embryo. Enlarged 2 X. C, calcarine fissure; V, posterior horn of lateral 

 ventricle. 



A frontal section through the temporal region about midway 

 between the frontal and occipital pole showed the matrix sur- 

 rounding the ventricle to be in a state of great activity. The 

 'Ubergangschicht' is here distinctly stratified and the four layers 

 described by His as developing between the third and fourth 

 month can be easily seen. The white matter between the closely 

 packed collection of neuroblasts and the cortex is thickly strewn 

 with migrating cells. 



