VASCULARITY OF THE CEREBRAL CORTEX 205 
Kappers (loc. cit.) offers a suggestion, in another connection 
altogether, which seems to provide a very plausible explanation, 
at least in part, for the special vascular richness of the lamina 
granularis, and perhaps also of the sensory nuclei. In discussing 
the importance of the granule cells in relation to his principle 
of neurobiotaxis, he points,out that, “while in projection cells 
the nervous current is directly realized and led away, on the 
contrary, in the granular cells with short axis cylinders forming 
an intricate network the stimulation is kept within a certain 
region.”’ He goes on to point out that the long ascending and 
descending tracts very often end in relation with such cells, 
citing among other examples the case of the sensory root fibers 
ending in the medulla oblongata ‘‘and (less general) in the cord.” 
Such a region of concentrated or localized activity might reason- 
ably be expected to have a relatively rich blood supply, and no 
doubt this is one at any rate of the factors giving rise to the 
observed differences. 
To facilitate comparison of the vascularity of the cerebral 
cortex with that of the lower centers previously studied, table 
3 has been prepared. In this table all the values have been 
reduced to the basis of a cube of tissue of 100 » edge, so that 
the figures given represent the total length of the capillaries in 
a block of tissue of volume 1,000,000 c. u, or 0.001 ec. mm. This 
not only makes easy the direct comparison of the figures in 
the table, but also provides a unit with which comparisons 
may readily be made in future studies. It may be remarked 
that the ratios in the table were calculated from the original 
readings, not from the reduced figures which are tabulated 
beside them. These ratios show that, on the whole, the vascular 
supply of the cortex is not much greater than that of the ventral 
cornu of the gray matter in the spinal cord, but exceeds that of 
the ventral funiculus of the white matter from three and a half 
to over seven times. 
It will be observed that the vascularity of the insular cortex 
corresponds roughly with the values obtained for the motor 
centers, while the various laminae in the other areas cover about 
the same range as the sensory and correlation centers in the lower 
