The effect of altitude 265 



C0 2 pressure and the corresponding rise in oxygen pressure which we 

 have already discussed. The beneficial effect of exercise at high 

 altitudes is of course commonplace amongst the persons who frequent 

 mountains, and especially the benefit derived from going up a little 

 higher than the point at which one is living, and then coming down 

 again. Our results show that this benefit is no intangible affair which 

 may be vaguely included under the general term "training," but that 

 it is a very definite change in the blood of the individual which may 

 be detected by the chemical analysis of that fluid. 



There is no difficulty then in stating the reason why I should 

 have become acclimatised when I walked up the mountain and not 

 when I went up on the mule in the former case the effort of the 

 climb induced oxygen want and consequently acid production, in 

 the latter case this element was absent. 



To answer the other of the two questions set above, why did I not 

 become accommodated at Teneriffe when Douglas did so ? is at first 

 sight more difficult, as the consideration of mountain sickness is bound 

 up with that of exercise at high altitudes. I will postpone the answer 

 till the next chapter. 



REFERENCES 



(1) Boycott and Chisholm, Biochemical Journal, v, p. 23, 1911. 



(2) This research is published in abstract in the Physiol. Proc. ; Journal of Physiol. 



XLV, p. xl, et seq. and will be sent for publication in extenso to the Philo- 

 sophical Transactions of the Royal Society. 



(3) Ryffel, Physiol. Proc. ; Journal of Physiol. xxxix, p. v, 1909. 



(4) See also Aggazzotti, Arch. ital. de Mol. XLVII, pp. 54, 66 ; Galleotti, Arch. ital. 



de biol. XLI, p. 80. 



(5) Barcroft, Physiol. Proc. ; Journal of Physiol. XLVI, p. xxx, 1913. 



(6) Campbell, Douglas, Haldane and Hobson, Journal of Physiol. XLVI, p. 301, 1913. 



