230 CHANGES IN CIRCULATORY MECHANISM 



metabolism of the organs. Part is probably due to the nervous 

 exaltation produced by the bracing air, the new conditions of life, 

 &C. 1 Loewy, however, did not find that a sojourn at a bracing 

 seaside place had a similar influence. Some writers have attri- 

 buted the increase to the electrical potential of mountain peaks, 

 but have adduced no convincing evidence. 



By lower oxygen tensions than 40 mm. Hg in the alveolar 

 air, the metabolism of the cells becomes deranged. The respira- 

 tory quotient rises, lactic and oxalic acids appear in the urine, 

 and the alkalescence of the blood sinks. The living protoplasm 

 obtains its oxygen from the less organised substances in the body. 

 Such decomposition is signalised also by the fatty degenera- 

 tion of the tissues and by an increased nitrogen output. The 

 latter rose 75 per cent, in a dog submitted for 7 hours to 

 230 mm. Hg (Fraenkel and Geppert). 



CHANGES IN THE CIRCULATORY AND RESPIRATORY MECHANISMS 

 OCCURRING IN HlGH ALTITUDES 



A diminution in the barometric pressure has no mechanical 

 effect on the circulation or respiration. The fluids of the body 

 equally transmit the change of pressure to all parts. The blood 

 pressure has been measured and found to be unchanged at a 

 pressure corresponding to an altitude of 6000-7000 m. 



If the pulse is accelerated, the respiration quickened and deepened, 

 these results are due to chemical and not mechanical causes. The 

 pulse frequency is always increased in high altitudes, and especially 

 when work is performed. A soldier in Turin raised 5 kg. dumb-bells 

 at 4" intervals 121 times, and his pulse increased from 62-68. On 

 Monte Rosa he raised the bells 119 times, and his pulse increased 

 from 94-120. 



Cheyne-Stokes respiration and irregular depth of respiration 

 commonly occurred in men sleeping or resting on Monte Rosa, 

 and are probably to be ascribed to the diminished tension of C0 2 

 in the alveolar air. Haldane has shown that the rhythm of 

 respiration is normally controlled by the C0 2 tension in the 

 alveoli, and that this tension is kept remarkably constant. 



1 Aggazzotti failed to find any increased O a use or CO 2 output in guinea-pigs 

 kept at high altitudes. 



