206 EDWARD HORNE CRAIGIE 
part of the brain, though the richest part of the cortex studied 
is slightly poorer than the richest center lower down—the dorsal 
cochlear nucleus. May it be that, great and intense as the 
activity of the cortex probably is, that activity is nevertheless 
more intermittent in any one area than is the activity of the 
lower sensory nuclei? The latter, as was pointed out in the 
previous paper, are in more or less constant receipt of stimuli, 
but only a small proportion of these give rise to any reflex, 
and only a still smaller proportion, when any, reach the cerebral 
cortex. Many impulses are, no doubt, generated within the 
cortex itself, and such generation may possibly involve a greater 
expenditure of energy than the mere passage of an impulse 
caused by a stimulus somewhere else, so that the cortex may 
reasonably be expected to be relatively rich in most areas; but 
the activity in any one portion of the cortex is probably less 
constant than that in a sensory nucleus, so that greater vas- 
cularity is not required. 
It might perhaps be mentioneu here that what appears to 
be a clear example of a direct relation between vascularity and 
functional activity has been described recently in Cajal’s labo- 
ratory by De Castro (’20), who found such a relation distinctly 
shown in comparing the vessels belonging to the olfactory 
glomeruli in man with those in macrosmatic animals. 
It may be remarked that, while the ‘motor cortex’ (regio 
praecentralis) ranks low among the five areas studied, it is very 
little poorer than the oceipital and temporal areas, and is con- 
siderably richer than the regio insularis. 
Finally, we note that the values obtained for the vascularity 
of the lamina zonalis in the four richer areas are very similar 
to the figure representing the condition in the molecular layer 
of the cerebellar cortex. 
As in the previous study, the results for-the two sexes have 
been separated and averaged, and the comparison of these is 
made in the charts in figure 4. The difference between the 
sexes is much more definite than it was found to be in the lower 
centers, the vascularity in the males being greater in every 
lamina of the parietal, temporal, occipital, and praecentral 
