1922] on Physiological Effects at High Altitudes in Peru 617 



"normal." (The partial pressure of oxygen forms the abscissa.) 

 At the sea level the oxygen pressure in the lung is about 100 mm. 

 and the quantity of oxygen in the blood 96 per cent, of the possible 

 load. (See the point A on the graph.) 



(c) Until recently it was supposed that the curve did not alter, 

 and therefore the graph labelled " Xormal " stood for all altitudes. 



(d) Also the most competent authorities regarded an oxygen load 

 of about 90 per cent, of the possible maximum as being required for 

 the conduct of life — apart from short exposures. 



(e) The probable partial pressure of oxygen in the lungs at 

 25,000-30,000 ft. is calculated by a process of exterpolation to be 

 about 30 mm. Combining c, d and e above, the quantity of oxygen 

 in the arterial blood on Everest would be 58 per cent, of the 

 maximum — far below that necessary. 



(/) The recent expedition to Cerro cle Pasco has brought out 

 two new points : — 



(1) That natives lead a reasonably normal existence with blood 

 charged only up to 82 per cent, of the possible, and Europeans with 

 8b per cent, of the possible, load of oxygen. 



(2) That the graph changes in position, and for natives and 

 Anglo-Saxons approximates to that labelled Cerro (14,000). 



(g) On this graph a partial pressure of 70 mm. of oxygen in the 

 lung might saturate the blood up to 67 per cent. (c). 



(h) It is scarcely likely that the curve moves further than that 

 marked " Probable limit (30,000 ft.)." On that curve, however, 

 the blood would be charged up to 76 per cent. — a figure within a 

 reasonable distance of what has actually been observed in the Andes. 



[J. B.] 



•2x2 



