It is known that many organs have the property of oxidizing the fatty acids. By means of perfusion experiments it has been demonstrated that the liver (Embden et al.) and the kidney (Snapper and Grünbaum) oxidize the fatty acids in the beta position: the liver forms large amounts of β-hydroxybutyric acid and of aceto-acetic acid, which are destroyed only to a small extent, while the kidney has a strong oxidizing effect also on the acetone (ketone) bodies. Organ extracts have likewise been found capable of oxidizing fats. Liver extracts contain enzymes capable of oxidizing β-hydroxybutyric acid to aceto-acetic acid or reducing the latter to β-hydroxybutyric acid (Wakeman and Dakin) and also, according to Kühnau, of destroying β-hydroxybutyric acid and forming dicarboxylic acids by oxidation of aceto-acetic acid. Aceto-acetic acid is partially reduced by minced kidney to β-hydroxybutyric acid (Embden and Michaud). Dehydrogenases of the higher fatty acids have been found in the pancreas and the intestine (Tangl and Berend) and in the bile and the fatty tissue (Quagliarello), in the liver (Mazza and Stolfi), and in the kidney (Mazza).