Practically all cytological structures and all enzymatic activities demonstrable by specific staining procedures show quantitative differences among the parenchymatous cells, dependent upon their position in the lobule. Distribution of the organelles within each parenchymatous cell is probably related to the direction of molecular movement within the cell, and the quantitative differences among adjacent cells probably reflect the direction of blood flow within the hepatic lobule. These differences suggest that oxidative respiration via the Krebs cycle may operate at a high level in the peripheral cells of the lobule, and that glycolysis and other oxidative activities may occur at relatively high rates in the centrolobular cells.