262 Chapter XVII 



For the purpose of the present calculation C A may be neglected, 

 it is under half a millimetre and therefore we may say as an approxi- 



Q 



mation that ^- ^~- is constant. 

 VA - Uv 



Let us see by a specific example the bearing of this constancy on 

 the question. In Teneriffe at the sea-level Douglas's alveolar CO 2 

 (CV) pressure was 41 mm., his respiratory quotient was 75, therefore 



41 



(0 A O V ) was ._- =51. The value of A was 160mm., or corrected 

 '/5 



for the pressure of aqueous vapour in the lung 150 mm., therefore 

 O A = 99 mm. Now at the Alta Vista hut, where the barometer was 514, 

 the value of O A corrected for aqueous vapour in the lung is 104. 

 Had his C0 2 pressure been as before 41, O A O v would have been 51 

 and his alveolar oxygen pressure 53 ; but owing to the acclimatisation 

 which we have described his C0 2 pressure dropped to 32, and therefore 



32 

 O A O K was ^rr = 43, instead of 53, therefore his alveolar oxygen 



pressure would work out at 104 43 = 61 mm. * He had gained 

 10 mm. at this altitude, or one-sixth of his whole oxygen pressure by 

 the change of the distribution of acids in his blood. 



My own case afforded a control experiment. My carbonic acid 

 was scarcely altered as between the sea-level and 11,000 feet in 

 Teneriffe, with the result that my oxygen pressure at that altitude 

 was only about 49 50 mm., while that of Douglas was 61, a fact 

 which made a great difference to our comparative comforts at the 

 Alta Vista hut. This again was controlled by another observation. 

 For reasons of which I shall speak elsewhere, at Col d'Olen my 

 alveolar C0 2 did drop to 33 mm., my oxygen did reach 64 mm., whilst 

 later at Col d'Olen, after I had been up to the Margherita hut, where 

 my blood had acquired another dose of acid, displacing more C0 2 , 

 and had retained it after my return, my alveolar C0 2 pressure was 

 only 30 mm. and my oxygen up to 70 mm. Therefore, even allowing 

 a mm. or two for experimental error, my oxygen pressure was half as 

 much again as it had been at the Alta Vista. On my dissociation 

 curve the difference between 70 and 50 mm. is the difference between 



to be made. This may be done from a table found in the appendix copied from 

 Haldane's " Methods of Air Analysis." 



* These calculated values agreed very closely with the observed values, which 

 were 58'5 62'5 mm. 



