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Minute structure of thymus. Follicle of injected thymus from calf, four days old, slightly diagrammatic, magnified about 50 diameters. The large vessels are disposed in two rings, one of which surrounds the follicle, the other lies just within the margin of the medulla. (Watney.) A and B. From thymus of camel, examined without addition of any reagent. Magnified about 400 diameters. A. Large colorless cell, containing small oval masses of hemoglobin. Similar cells are found in the lymph glands, spleen, and medulla of bone. B. Colored blood corpuscles.