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01 October 1971
Vol 174, Issue 4004

About The Cover

Fox squirrel (Sciurus niger). The bones of these squirrels are stained red by uroporphyrin I, an abnormal porphyrin which accumulates because of a partial deficiency of the enzyme uroporphyrinogen III cosynthetase. A similar enzyme deficiency occurs in the human and bovine disease, congenital erythropoietic porphyria. See page 59. [Bill Clark, University of Maryland]