Oxygen consumption of unwashed fowl semen was manometrically determined in diluents containing 10% suspensions of extracts from the five regions of the hen's oviduct. Extracts from the magnum (and, to a lesser extent, from the infundibulum) augmented the respiratory rate of the spermatozoa. High mechanical pressure or homogenization of the tissue was required for extraction of the active substance(s). The active material appears to be of large molecular size, very likely protein in nature; it is not present, in significant amounts at least, in blood or egg albumen. The significance of the substance from the magnum in increasing the metabolic activity of fowl spermatozoa is discussed.