Comparison of retinal and cerebral vasculature in trypsin digest preparations.

The trypsin digestion technique for preparing flat mounts of the retinal capillary system was modified for comparable mounts of the cerebrocortical capillaries. These preparations, supplemented by electron microscopy, showed a basic similarity between the 2 systems, but the cortical capillaries have larger diameters, more abundant collateral channels, and less regularly spaced mural cells (intramural pericytes). The cortical capillaries did not show the right-angle branching of the precapillary arteriole characteristic of some retinal vessels, but they did show in the crotches of the branches an excess basement membrane that was not present in the retinal capillaries.