102 



RESPIRATORY MECHANISMS 



In dogs born and reared at high altitudes, Hurtado and 

 collaborators (1937, quoted from Dill, 1938) have found also 

 a very considerable increase in muscle haemoglobin over that 

 found in dogs at sea level. It would be interesting to learn 

 whether such an increase can be brought about in mature 

 individuals. 



The amount of work which can be performed by a fully 

 acclimatized person decreases with increasing height and is a 

 function of the maximum amount of oxygen which can be ob- 

 tained by the most violent ventilation. As seen from the 



Fig. 58. Approximate amount of oxygen that a man can obtain and utilize 

 for climbing (ordinate right) at all altitudes between sea level and the summit 

 of Mount Everest. (Y. Henderson.) 



accompanying graph, reproduced from a very instructive re- 

 cent summary by Y. Henderson (1939), the power of climb- 

 ing is reduced to below the summit of Mount Everest. 

 Acclimatization to high altitudes does not improve the power 

 for work at sea level, but reduces it, because the lowered 

 alkali reserve will demand a more rapid circulation and a 

 larger ventilation to eliminate the same amount of C0 2 

 without unduly acidifying the blood. 



Variable environments. On pp. 10, 14 it was set forth in some 

 detail that the air in the upper strata of the soil and many 

 temperate fresh waters may occasionally show very low oxy- 



