This book describes the respiratory function of the lungs in a variety of circumstances and indicates how the function can be assessed. The function includes lung ventilation, gas exchange and lung perfusion with their respective physiological control mechanisms. The circumstances include the resting state, sleep, exercise, abnormal environments and diseases of the lung and other organs. The applications are in respiratory medicine including lung function laboratories and in paediatrics, geriatrics, environmental, occupational and sports medicine and medico-legal work. The material that has been assembled is also likely to be of use to non-respiratory physiologists, bio-engineers, ergonomists, anthropologists and other scientists.