1022] on Physiological Effects at High Altitudes in Peru 615 



more oxygen when exposed to rare atmospheres than is the case with 

 normal blood. 



5. We sought in vain for any such form of acclimatisation as 

 might be afforded by the driving of an increased volume of blood 

 round the body in unit time. A rather natural supposition would 

 be that, if the haemoglobin of each cubic centimetre of blood were 

 deficient in oxygen, the tissues might be fed with sufficient oxygen 

 by the simple process of giving fchem more blood ; but this is not so. 



Fig. 2. 



Ifc is true the heart quickened with exercise, but the quickening 

 seems to have been rather a signal of distress that a compensatory 

 mechanism. 



Three principal forms of compensation have been described : 

 they are increased total ventilation, increased expansion of the chest, 

 increased haemoglobin, and increased affinity of the blood for oxygen ; 

 their relative importance is a matter for future research. Jointly or 

 severally they may mitigate the effects of oxygen want, but they 

 cannot entirely abolish them ; at some altitude the human frame 



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