VASCULARITY OF THE CEREBRAL CORTEX AlN 
the relative vascularity of various parts of the cerebellum, 
medulla oblongata, and spinal cord. 
2. The relative vascularity of the five laminae in a single 
region is found to be similar in all the cortical areas examined, 
the lamina granularis interna (IV) being the richest in every 
case. 
3. The supragranular layers show a tendency to be a little 
richer than the infragranular ones, the poorest layer being the 
lamina multiformis (VI) in every area except the insular, where 
the lamina zonalis (I) is very slightly poorer. 
4. It seems probable that the granular and supragranular 
layers are receptive and associative in function, while the infra- 
granular layers give rise to corticifugal fibers. This suggests a 
comparison with the lower centers, where the sensory and cor- 
relation nuclei were found to be more richly vascular than the 
motor nuclei. Moreover, it has been suggested that the lamina 
granularis interna is composed of relatively less highly differ- 
entiated cells than the other layers, which gives rise to specula- 
tion as to why it should be more vascular than the remaining 
laminae. 
5. The average vascularity of the five layers is the same in 
the occipital and temporal areas, and is only slightly less in the 
praecentral region. The parietal area is distinctly richer than 
the others, while the insular cortex is much the poorest. 
6. The vascularity of the five laminae in the insular cortex 
covers about the same range as that of the various motor centers 
studied in the brain stem and spinal cord (table 3), while the 
vascularity of the other areas corresponds approximately to 
that of the sensory and correlation nuclei. 
7. The vascularity of the cerebellar cortex is of about the 
same order of magnitude as that of the cerebral cortex taken 
as a whole. 
8. Sexual and racial differences appear to be more marked in 
the cortex cerebri than in the parts of the central nervous system 
previously studied, suggesting that the vascularization of the 
more recently evolved centers is more susceptible than that of 
more ancient regions to sexual, hereditary, or environmental 
influences. 
