The most famous work in the history of altitude physiology, in which Bert proved that the principal symptoms of altitude sickness arise from reduced partial pressure of oxygen and not from diminution of total pressure. Bert introduced oxygen apparatus to avert the dangerous consequences of ascent to high altitudes, and was the first to study the conditions of high-altitude ascents in a pressure chamber. He also explained the etiology and mechanism of caisson disease. English translation, 1943. See No. 12192.