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Abstract
The initial development of retinal vessels in the rat was studied by light and electron microscopy. In the 15-day-old rat embryo undifferentiated cells derive from the outer wall of the hyaloid vessel, or the immediate surrounding tissue, and migrate into the peripapillary retina beneath the internal limiting membrane. No vascular budding is evident. The cells proliferate, form a network, and then evolve into lumenized vessels. Initially the vascular network is capillary in nature, and there is no evidence that development of veins precedes that of capillaries. Similar observations made by earlier authors are discussed in relation to our own work.