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The Physiological Effects of Loiv Atmospheric Pressures, as 

 Observed on Pikes Peak, Colorado. [Preliminary Com- 

 munication.) 



By 0. Gordon Douglas, B.M., Fellow of St. John's College, Oxford ; 

 J. S. Haldane, M.D., L.L.D., F.B.S., Fellow of New College, Oxford ; 

 Yandell Henderson, Ph.D., Professor of Physiology, Yale University 

 Medical School; and Edward C. Schneider, Ph.D., Professor of 

 Biology, Colorado College. 



(Received January 11, — Read January 18, 1912.) 



The following is a short preliminary account of a series of observations 

 made in the summer of 1911 on the summit of Pike's Peak, Colorado. 



Pike's Peak is 14,109 feet above sea-level, the barometric pressure on the 

 summit being about 18 inches (457 mm.). There is an excellent stone house 

 close to the summit, in which we were accommodated during our stay of 

 five weeks. The main object of the expedition was to discover to what 

 extent, and by what means, adaptation takes place to low barometric pressure 

 and consequent deficiency in the partial pressure of oxygen in the air. 



Our chief conclusions are as follows : — 



(1) After two or three days on the summit of Pike's Peak very distinct 

 signs of acclimatisation began to appear. 



(2) Before acclimatisation occurred blueness of the lips and face, nausea, 

 intestinal disturbance, headache, fainting in some persons, and periodic 

 breathing were observed, besides great hyperpncea on exertion or holding 

 the breath for a few seconds. 



(3) All these symptoms are referable, directly or indirectly, to want of 

 oxygen, produced by the diminished partial pressure of oxygen in the air. 

 We did not observe, either in ourselves or in the large number of persons 

 who ascended the Peak, any symptoms (apart from the effects of the bright 

 light) not referable to the same cause. 



(4) After acclimatisation had occurred these symptoms disappeared, with 

 the exception that hyperpncea on exertion or on holding the breath for 

 a few seconds was still much greater than usual. Periodic breathing was 

 still observed occasionally, and blueness of the lips and face was present after 

 continuous and fairly powerful exertion, such as walking up hill. 



(5) The respiratory exchange during rest remained about normal in the 

 one subject on whom exact experiments were made, and the respiratory 

 exchange during work did not appear to be markedly increased. 



VOL. LXXXV. — B. F 



