1922] on Physiological Effects at High Altitudes in Peru 613 



some degree of efficiency with the blood in this condition is of great 

 importance, because in recent years there has fbeen a tendency to 

 assume that a small degree of unsaturation of the arterial blood 

 must of necessity produce very grave results. Fig. 1 shows that 

 there is some adjustment of the blood to the new conditions. At 

 Cerro the unsaturation of the blood was written on the faces of the 

 inhabitants. Anyone who had any colour in his face was appreci- 

 ably cyanosed. 



2. Increased pulmonary ventilation has been shown by all recent 

 observers to be of great importance as a factor in adaptation to high 

 altitudes. In our case, had our respiration been the same in rate 



100 



80 

 ^ 40 



1^ 



20 40 60 80 lOOmm.ofHg, 



Part/el Pressure ofOxi/ger? rn thelvrrp 'a/wo//. 



Fig. 1. 



and depth at Cerro as it was at Lima we would have had about 

 40 mm. pressure of carbonic acid and 35 mm. pressure of oxygen in 

 the air of our lungs. In fact, owing to increased respiratory effort, 

 we reduced the carbonic acid to about 25 mm. and raised the oxygen 

 to about 52 mm. The importance of these facts is enhanced by the 

 certainty that it is the partial pressure of oxygen in the alveolar air 

 which regulates the degree of saturation of the blood. 



While the increased ventilation of the lung had been demon- 

 strated by previous observers, the mechanism which was responsible 

 for it had been much in dispute. This we investigated. The 

 mechanism of hyperncea at 7 est seems to be that first suggested by 



