RESPIRATION 



365 



centage of haemoglobin varies inversely with the barometric 

 pressure, and that even quite small diminutions in barometric pres- 

 sure are effective in causing a rise in the haemoglobin percentage. 

 In different individuals, however, the effects on the haemoglobin 

 percentage of a given diminution in barometric pressure vary 



Figure 96. 

 Average haemoglobin percentages in persons living 

 permanently at different altitudes (FitzGerald). 



considerably. Thus among the persons acclimatized on the 

 summit of Pike's Peak (barom. 453 mm.) the rise in haemoglobin 

 percentage varied from 13 to 53 per cent of the normal. The rate 

 at which the haemoglobin percentage rises when a person goes to 

 a high altitude varies also. In some persons the rise is very slow ; 

 and in consequence of this some observers have failed to detect 

 any rise on going for a short time to a high altitude. 



As the average rise in haemoglobin percentage is appreciable 



with only small increases of altitude, one would expect to find 



that with increase of atmospheric pressure above normal the 



haemoglobin percentage would fall below the normal value at 



sea level. That this is actually the case was shown for dogs and a 



I monkey by A. Bornstein, who kept the animals under atmospheric 



I pressure of about three atmospheres or 2,280 mm. in the Elbe 



I tunnel at Hamburg during its construction.^ She found that the 



I ''Adele Bornstein, Pfluger's Archiv., 138, p. 609, 191 1. 



