14 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 00 



greater diminution. So long as there is present a partial pressure 

 of oxygen sufficient to change most of the haemoglobin of the venous 

 blood into oxyhemoglobin during its passage through the lungs, 

 there can arise no lack of oxygen. 



At sea-level the pressure of oxygen in the pulmonary alveolar air 

 is about ioo mm. Hg. Exposed to only half this pressure, the 

 haemoglobin is more than 80 per cent saturated with oxygen. 



In noted health-resorts of the Swiss mountains the barometer 

 stands at such a height that the concentration of oxygen is far less 

 than in the most ill-ventilated room. On the high plateau of the Andes 

 there are great cities ; Potosi, with a hundred thousand inhabitants, 

 is at 4,165 meters, and the partial pressure of oxygen there is about 

 13 per cent of an atmosphere in place of 21 per cent at sea-level. 

 Railways and mines have been worked up to altitudes of 14,000 to 

 15,000 feet. At Potosi girls dance half the night, and toreadors 

 display their skill in the ring. On the slopes of the Himalayas 

 shepherds take their flocks to altitudes of 18,000 feet. No disturb- 

 ance is felt by the inhabitants or by those who reach these great 

 altitudes slowly and by easy stages. The only disability to a normal 

 man is diminished power for severe exertion, but a greater risk 

 arises from want of oxygen to cases of heart disease, pneumonia, 

 and in chloroform anaesthesia at these high altitudes. The new- 

 comer who is carried by the railway in a few hours to the top of 

 Pike's Peak or the Andes may suffer severely from mountain sick- 

 ness, especially on exertion, and the cause of this is want of oxygen. 

 Acclimatization is brought about in a few days' time. The pulmonary 

 ventilation increases, the bronchial tubes dilate, the circulation be- 

 comes more rapid. The increased pulmonary ventilation lowers the 

 partial pressure of carbon dioxide in the blood and pulmonary air, 

 and this contributes to the maintenance of an adequate partial pres- 

 sure of oxygen. Haldane and Douglas * maintain that the oxygen is 

 actively secreted by the lung into the blood, and find that the number 

 of red corpuscles and total quantity of the haemoglobin increase, but 

 the method by which their determinations have been made has not 

 met with unqualified acceptance. 2 Owing to the combining power of 

 haemoglobin the respiratory exchange and metabolism of an animal 

 within wide limits is independent of the partial pressure of oxygen. 

 On the other hand the process of combustion is dependent on the 



1 Phil. Trans. Roy. Soc. B., Vol. 203, p. 185, 1912; and Fitzgerald, ditto, p. 351. 



2 Cf. Dreyer, Ray & Walker, Skand. Arch, fur Physiologie, Bd. 28, p. 299, 

 I9I3- 



