From the early 17^th century the advent of physical and chemical sciences developed two important movements toward the explanation of all vital phenomena: the Iatrochemical and Iatromechanical School. The important research of their representatives as Jan Baptist van Helmont, John Mayow, Robert Boyle, Gian Alfonso Borelli, Richard Lower and Albrecht von Haller, followed by the discovery of the atmospheric gases, provided a fecund soil for the leading work of Lavoisier in respiratory physiology.