108 E. LINDON MELLUS 



tion of the cortex I find the hne of demarkation between the first 

 or molecular and the second (external granular layer of Mejniert) 

 very striking, composed almost entirely of small round deeply 

 stained granules. This hne is less pronounced on the crest of the 

 convolution than within the fissure, both on the walls of the fis- 

 sures and at the base. The stain is most intense at the base of 

 the fissure and becomes gradually paler as we approach the sur- 

 face of the brain. The sharp definition of this line seems to be 

 due partly to the deeper stain taken by these small granules and 

 partly to their being very closely packed. But on the crest of the 

 convolution the stain of the same cells is distinctly fainter. 



The appearance of so many cells in the white matter at this 

 late stage of intra-uterine life naturally led to further investiga- 

 tion. The available material was by no means perfect. It 

 consisted of a somewhat fragmentary brain from which the brain 

 stem and the basal ganglia had been removed, and the least injured 

 portion of the ventricle was the occipital end. The matrix sur- 

 rounding the posterior horn of the lateral ventricle was in the 

 greatest activity, throwing off neuroblasts in enormous numbers 

 (fig. 1). There was still present between the ventricle and the cor- 

 tex the layer of neuroblasts called by His the 'Ubergangschicht.' 

 Between this and the cortex the corona radiata was full of partly 

 developed cells and naked nuclei apparently streaming towards 

 the cortex in more or less radial lines. From the matrix broad 

 streams of nuclei led more or less directly to the 'Ubergang- 

 schicht.' These streams were not everywhere radially directed, 

 but for a certain distance ran parallel to the wall of the ventricle. 

 In cross section the formation of the ' Ubergangschicht' was 

 distinctly outhned, completely surrounding the ventricle except 

 in that portion contiguous to the calcarine fissure, where the 

 matrix more nearly approached the resting stage. Here the cor-, 

 tex of the calcarine fissure in its entire extent was much more 

 deeply stained than the cortex on the external surface of the con- 

 volutions and the 'Ubergangschicht' was not present. At each 

 extremity of the long narrow slit representing the posterior horn 

 of the lateral ventricle the broad band of deeply stained nuclei is a 

 prominent object in the section clearly visible to the naked eye. 



