Fraenkel and Geppert3 placed a dog which had fasted seven days under the influence of greatly diminished atmospheric pressure and found an increased protein metabolism which continued on the second and third days. They also suspected the presence of products of incomplete combustion in the urine. These results accord with Araki's investigations.

Von Terray4 finds no change in the respiratory activity of dogs in air containing between 87 and 10.5 per cent, of oxygen. When 10.5 per cent, of oxygen is present an increased respiratory activity commences. With 5.25 per cent, of oxygen there is every indication of lack of oxygen for the tissues, and the elimination of lactic acid in the urine is pronounced. The quantity of lactic acid eliminated was greatest after the respiration of an atmosphere containing 3 per cent, of oxygen. The quantities obtained were 1.206, 1.860, 2.176, 2.300, 2.352, 2.663, 3.020, and 3.686 grams of lactic acid in twenty-four hours. In these cases we again see the analogy of the metabolism to that already cited as having been discovered by Araki after bloodletting in rabbits.

1 Douglas, Haldane, Henderson, and Schneider: "Transactions of the Royal Society," 1912, Series B, cciii, 185.

2 Durig and Zuntz: "Archiv fur Physiologie," 1904, Suppl., p. 421. 3 Fraenkel and Geppert: "Ueber die Wirkungen der verdunnten Luft,'. 1883.

4 von Terray: "Pfluger's Archiv," 1896, lxv, 440.

L. Zuntz1 found that when he respired in a pneumatic cabinet, at an atmospheric pressure of 448 mm. of mercury there was no change in his respiratory metabolism as compared with the normal. The results may be tabulated as follows:

This latter experiment was done at a pressure corresponding to a mountain height of 4500 meters. He also showed that variations in atmospheric pressure within the above limits had no effect on the metabolism during muscular exercise.

This work was repeated by Hasselbalch and Lindhard2 in an experiment which lasted twenty-six days. During fourteen days a man remained in a pneumatic cabinet at an atmospheric pressure of 455 mm. The consumption of oxygen and the urinary ammonia and amino-acids were unaffected by this influence.

Von Schrotter and Zuntz3 made two balloon ascents to heights of 4560 and 5160 meters. Zuntz showed an increased oxygen absorption of 7 per cent, above that at sea-level. In the case of Von Schrotter the increase was slight except during one interval of shivering, when a 20 per cent, increase was recorded. The authors attributed the slight rise in the metabolism to the increased work done by the respiratory muscles. During the higher ascent sugar appeared in the urine of Zuntz, indicating incomplete oxidation.

A research of Zuntz4 on the subject of mountaineering describes how he and Durig ascended to the Col d'Olen (2900 meters), and, having remained there for a week, passed upward to a hut (4560 meters) constructed near the summit of Monte Rosa, the highest mountain of the Alps after Mont Blanc. They lived in this hut two weeks and a half. The height of the barometer was 443 millimeters, which indicates a quantity of oxygen amounting to 12.2 per cent, of an atmosphere. On the Col d'Olen there was no increase in their metabolism when they were resting, and there was no increase in the requirement of energy necessary to accomplish one kilogram-meter of work. This agrees with the results of Burgi elsewhere mentioned (p. 332). At the higher level, near the summit of the mountain, the resting metabolism increased at once and permanently to the extent of 15 per cent. Zuntz during a former sojourn had noted an increase of 44 per cent, in his metabolism when on the mountain. Exposure to the sunlight was almost without effect on the metabolism. The increased metabolism was not due to cold, for it was present when the individual was in a warm bed in the hut. At sea-level the energy equivalent of 3 kilogrammeters is liberated in the body in order to lift 1 kilogram of body substance 1 meter high. Here on the snow-fields of Monte Rosa Durig required the equivalent of 4.0 to 4.8, Zuntz 5.3 to 6.8 kilogrammeters of energy to accomplish 1 kilogrammeter of work. This agrees with a former experiment of Zuntz when he was living in the same locality, in which he found the increased metabolism necessary to effect 1 kilogrammeter of work in climbing was 70 per cent, above the requirement for the same work at sea-level.

1 Loewy and Zuntz: "Pfluger's Archiv," 1897, Ixvi, 477. 2 Hasselbalch and Lindhard: "Biochemische Zeitschrift," 1914, lxviii, 265 and 295.

3 von Schrotter and Zuntz: "Pfluger's Archiv," 1902, xcii, 479. 4 Durig and Zuntz: "Archiv fur Physiologie," 1904, Suppl., p. 417.

Hasselbalch and Lindhard,1 while noting that the ultraviolet rays of the sun reduce the frequency and increase the depth of respiration, find that exposure to the effect of such rays in the high Alps (Brandenburger Hut, 3290 meters) has no effect upon the metabolism (see p. 150).

Not only is the metabolism necessary to accomplish work greater on high mountains than at sea-level, but the capacity for work is greatly reduced. Schumburg1 found that he could accomplish a maximum of 999 kilogrammeters of work in one minute in Berlin, 619 when on the Monte Rosa glacier, and only 354 kilogrammeters when he was on the top of the mountain. The limit of work on Monte Rosa was, therefore, one-third what could be accomplished in Berlin, probably on account of the accumulation of imperfectly oxidized products of metabolism, which reduces the muscular power.2

1 Hasselbalch and Lindhard: "Skan. Archiv fur Physiologie," 1911, xxv, 361.

Durig and Zuntz, Mosso, and others have found their respiration to be distinctly of the Cheyne-Stokes character after a return to the hut subsequent to exercise in the higher Alps. They found that when they were on Monte Rosa a temporary oppression resulted if their respiration was partly hindered - as in the case of lacing their boots. Also strict attention to a definite task might reduce the respiratory activity to such an extent that anemia of the brain, accompanied by dizziness, readily ensued.