The Structure of Normal Small Lymphatics

The structure of the lymphatic capillaries and lacunes as seen by electron microscopy was similar to that of the blood capillaries of, for instance, skeletal muscle. All the lymphatic endothelial cells contained many vesicles and caveolæ intercellulares. No fenestrations in the endothelium were seen, but some intercellular junctions were patent, especially in diaphragmatic lacunes. The basement membrane was less regular than that of blood capillaries or of mesothelium and in many places, especially in diaphragmatic lacunes, it appeared to be absent. Carbon and ferritin were injected into the peritoneal cavity and could be seen in the lumen of diaphragmatic lacunes, in vesicles in mesothelium and endothelium, and in patent junctions between endothelial cells. Deposits of ferritin without an encircling membrane were also seen in the cytoplasm.