RESPIRATION. 395 



Bert has shown that air under the pressure of seventeen atmos- 

 pheres, or pure oxygen at a pressure of three and a half atmospheres, 

 will produce in animals convulsions resembling those of strychnia, 

 and death ensues. It is the oxygen itself that kills, due to its being 

 compressed. 



Mai de Montagne, Rarefied Air. All travelers who have climbed 

 the Alps speak of the same troubles experienced by them at nearly 

 the same altitude: a considerable diminution of appetite, a disgust 

 for food, nausea and even vomiting, palpitations, headache, lassitude, 

 sleepiness, and buzzing in the ears. This state is known as anoxy- 

 haemia, or want of oxygen in the blood. Dyspnoea takes place not 

 only because the air inspired contains oxygen in a given volume, but 

 also because the dissolution of this gas in the blood is less easy under 

 feeble pressure. Muscular work in the ascent also uses up consider- 

 able of the oxygen taken in. At 10 per cent, of an atmosphere there 

 ensue restlessness and dyspncea, and, at about 7 per cent., death. A 

 partial pressure, like 7 per cent, of an atmosphere, corresponds to 

 an altitude of 30,000 feet. Men in a balloon have ascended about 

 28,500 feet. 



In respiration at low pressure Boycott and Haldane in their 

 experiments could not support Mosso's theory that mountain sickness 

 was due to lack of C0 2 (acapnia). The relief produced by the excess 

 of C0 2 is due at least mainly to the artificial production of an abnormal 

 hyperpncea and consequent rise in the alveolar C0 2 pressure. The 

 condition of the body then becomes one of hypercapnia, and indeed 

 hypercapnia may be said to be already present at high altitudes with 

 the addition of C0 2 to the inspired air, since the stimuli to the res- 

 piratory center are already in excess of normal. 



Haldane and Poulton made experiments with a steel chamber in 

 which the pressure of the air was reduced to that which prevails in the 

 Alps. They found that the great hyperpncea produced by a rapid fall 

 in the oxygen pressure of the inspired or alveolar air is not due to a 

 direct effect of want of oxygen on the respiratory center, but to that of 

 preformed carbon dioxide present to start with in the blood, the 

 action of this carbon dioxide being reinforced by that of acid or other 

 products produced by the want of oxygen, so that the threshold pres- 

 sure at which the carbon dioxide excites the center is lowered. If 

 sufficient of the preformed carbon dioxide is first removed by forced 

 breathing, want of oxygen has no exciting influence on the respiratory 

 center and apncea may be produced in the presence of want of oxygen. 



The question arises, How do the inhabitants of high mountains 



