1911 Encyclopædia Britannica/Excretion

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EXCRETION (Lat. ex, out of, cernere, cretum, to separate), in plant and animal physiology, the separation from an organ of some substance, also the substance separated. The term usually refers to the separation of waste or harmful products, as distinguished from “secretion,” which refers to products that play a useful or necessary part in the functions of the organism.