Vascular permeability to collodidal carbon in chronically inflamed gingiva

The permeability of mechanically non‐irritated blood vessels of chronically inflamed gingivae of dogs was investigated using the carbon labelling method and electron microscopy. Deposits of carbon were found in the cytoplasm of endothelial cells and pericytes and in extravascular and intravascular leukocytes. The areas between the lining cells of the vessel wall and between these cells and the basement membrane did not reveal carbon particles. These results indicate that the vessels of resting chronically inflamed gingivae do not exhibit an increased permeability. Compared to healthy gingivae the chronically inflamed gingivae seem to be characterized by an increased emigration of leukocytes and an increased uptake of carbon by the cells of the vessel walls.