“…If the mammary gland arginase is, like that of the liver, concerned with deamination and urea production, with gluconeogenesis in fact, it should be possible to demonstrate (a) an uptake of aminoacids by the active mammary gland and (b) an output of urea. Arterio-venous studies, in fact, have uniformly shown a small but definite uptake of amino-acids by the 'lactating gland of the cow (Blackwood, 1932;Shaw & Petersen, 1938a, b; Bottomley & Folley, unpublished results) and the goat (Lintzel, 1934;Graham, Jnr., 1937-8;Graham, Jnr., Peterson, Houchin & Turner, 1937-8;Reineke, Peterson, Houchin & Turner, 1939) but not by the non-lactating bovine udder (Blackwood, 1932). An appreciable output of urea by the udder of the lactating goat has been reported by Graham, Jnr., Houchin & Turner (1937) and Reineke et al (1939).…”