Electron-microscopy, histology and the preparation of latex corrosion casts were the principal techniques employed. The terminal twigs of the portal and hepatic venous systems inter-digitate with one another, and are connected by a short network of sinusoids in both central and peripheral regions of the liver. The liver lobule is an elongated unit of hepatic cells with a polygonal cross-section containing a three-dimensional lattice of interconnected sinusoids. Lobules are not discrete vascular units as sinusoidal connections join them together. The parenchyma consists of anastomosing sheets of hepatic cells which enclose the sinusoids. Each sheet is two cells thick. Bile canaliculi are formed as intercellular spaces at the apices of three, four or five hepatic cells, and are surrounded by a condensed homogeneous zone of cytoplasm. They do not enclose individual cells (as in the mammal) but course between the two cell layers of the sheet. The electron-microscopical structure differs from that of the mammal in that the sinusoidal endothelium is fenestrated and partially discontinuous. Intercellular spaces frequently contain white blood cells. A basement membrane underlies the sinusoidal endothelium but it is poorly developed and, in many places, discontinuous.