EXACT knowledge of the mechanism, pathologic anatomy, genetic roentgenologic diagnosis and genetic reduction of fractures of the ankle is to be attained by combined experimental-surgical and experimental-roentgenologic investigations.1In this study the mechanism of fracture was determined by fracturing, the pathologic anatomy was ascertained by dissection, the genetic roentgenologic diagnosis was established by roentgen examination and the genetic reduction technic of the fractures was found by reduction maneuvers, which will be dealt with in a later paper, "Clinical Use of Genetic Roentgenologic Diagnosis and Genetic Reduction." In the experimental-surgical investigations free movability of the ankle joint is necessary in order to place the foot in the different positions which are to be considered. Experiments on cadavers were abandoned because of rigor mortis, which limits the movability of the foot and the ankle joint. The experiments have therefore been carried out exclusively on extremities which were amputated at the femur