In the early stages of work with oestrogenic and androgenic extracts, much consideration was given to the question of antagonistic or synergistic action between the two. Juhn, D'Amour, and Womack [1930] found no interaction between them when given simultaneously in the form of extracts to capons, but Schoeller and Gehrke [1933] later reported a synergistic action under these conditions. However, workers using crystalline substances have been unable to confirm these results. Callow and Parkes [1935], Morató-Manaro, Albrieux, and Buño [1935], and Gley and Delor [1937] agree in finding that the response of the capon comb to various androgens is decreased by the simultaneous administration of oestrogens. Mühlbock [1938] has shown that a daily dose of 5 mg. of oestradiol benzoate will completely abolish the response of the capon comb to 100 μg. daily of androsterone, and in a recent paper Emmens [1939a] produced curves showing the progressive decrease in