It is a well-known fact that the density of the capillary net work differs greatly throughout the central nervous system. The capillaries in the gray matter are much more abundant than in the white. There also exists a difference in the richness of capillaries within the gray matter itself. Pfeifer 's monograph ( '30) illustrates clearly the variation in the abundance of capillaries not only between the six cortical layers but also between the same layers of the different cortical zones ( fig. 4). The richness of capillaries varies in the different nuclei of the nervous system also. I n a recent communication on the angio-architecture of the substantia nigra ('36) it was shown that in its compact zone the nuclear cells were more dense than in the body of Luys while the capillaries in the former mere less dense than in the latter nucleus. Putnam ('37) remarked upon the relative sparseness of the capillaries in the substantia nigra. It can be said that, in a very general way, the richness of capillaries parallels the number of nuclear cells in any given region. One exception has been mentioned above and another is to be discussed in this paper. Physiolog-ically we know from the studies of Cobb and Talbot ( '37) and from the series of investigations on the pial vessels by Forbes a d his co-workers that the number of fnnctionallp active capillaries varies in the central nervous sptem. Recent studies by Alexander and Putnam ('37),
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.