. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . ft Fig. 2. Section through wall of hepatic sinusoid. Erythrocyte at right. Hepatic cell on left. Endothelium is in two layers. Pseudopod-like processes seen in lumen and between endo- thelial laminae. Magnification -^ 48,000. Trabecular cytoplasmic processes were recogniz- able only in transverse section where they appeared irregularly round, oval, triangular, etc. Some tra- beculae were situated between sheets of cytoplasm I'orming a bilaminar endothelial lining; others pro- jected into the lumen as pseudopods,
. Electron microscopy; proceedings of the Stockholm Conference, September, 1956 . ft Fig. 2. Section through wall of hepatic sinusoid. Erythrocyte at right. Hepatic cell on left. Endothelium is in two layers. Pseudopod-like processes seen in lumen and between endo- thelial laminae. Magnification -^ 48,000. Trabecular cytoplasmic processes were recogniz- able only in transverse section where they appeared irregularly round, oval, triangular, etc. Some tra- beculae were situated between sheets of cytoplasm I'orming a bilaminar endothelial lining; others pro- jected into the lumen as pseudopods, where some of them lay close to the sinusoidal lining, as though bent downstream by the moving blood (fig. 2). Among the trabeculae located in the lumen, some were lying in correspondingly-shaped grooves in larger masses of endothelial cell cytoplasm so that they did not bulge into the lumen, but presented one surface to it. In some instances the surface depression that lodged a trabecula was more than a groove; the lips of the "groove" were not fused together, but came into contact with one another above the trabecula, thus forming a tunnel through which the trabecula passed. Finally, many sections were seen in which a trabecula was fitted into a canal surrounded by a continuous wall of cytoplasm, the intercellular space appearing as a closed circular cleft. It will be appreciated from this "piston-in-a-cylinder"" arrangement that endo- thelial cells not only have elongate projections but also form internal channels into which such projec- tions can be fitted. Relation of endothelial cell to endothelial cell.— This relationship is easily described for those areas lined by thin sheets of cytoplasm. One process merely overlapped another, and the intercellular space apparently allowed blood plasma free access to the perisinusoidal space, as was evident from the fact that colloid particles passed between over- lapping cells with ease (5). In the vicinity
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