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Abstract
Presumably normal human corneal limbal tissue from five eyes, enucleated because of malignant tumors, was used in this study. The anterior area of the limbus, the only place where blood and lymphatic vessels and mast cells were found in the normal cornea, was studied with the electron microscope, and the fine structure described and discussed. The majority of the mast cells found in this area contained granules with a variable fine structure. Their constituents could be resolved into several main components: a finely particulate, a round, and a rodshaped component. It is thought that the round and rod-shaped sections are the same structure cut in different planes. Only a few mast cells contained granules of uniform structure, in which case they were composed mainly of the fine particulate material, the particles of which were sometimes arranged in an orderly fashion, giving a quasilamellar appearance. Most of the limbal blood capillaries had a thick-walled endothelium. Some, however, possessed localized thin-walled areas with or without fenestrations. Such fenestrations were not patent pores, but were closed by a thin membranous diaphragm. The basement lamina, variable in thickness, generally consisted of one to several layers of alternating dense and less dense material. The lymphatic capillaries were characterized by their poorly developed basement membrane, thin endothelial cells, except near nuclei, absence of fenestrations, corpuscles within the lumen, and pericytes.