Abstract
A graphical analysis of the mechanical contribution of the thoracic and abdominal components during different kinds of breathing cycles has been made. The lung volume has been plotted against the dynamic pressures above and below the diaphragm; the intrathoracic pressures due to the elasticity of the lung and of the chest were also represented on the same diagrams. The transdiaphragmatic and the transabdominal pressures have been thus studied and compared with the pressures exerted by the inspiratory and expiratory muscles as given by transthoracic pressure measurements. Submitted on February 27, 1961