CHAP. XIX. THE EFFECT ON RESPIRATION. 375 



From the ' permanent ' effects there is no escape. The large 

 increase in the rate of respiration and the compnlsory breathing 

 through open mouths were caused by involuntary efforts to make 

 up for the decrease in the density of the air by imbibing a greater 

 voliome. It was possible, without any great effort, at a pressure of 

 14*750 inches (19,600 feet), to sustain life, while at rest, by increas- 

 ing the volume of air inspired, and thus in some measure to 

 compensate for the reduction in its density (which was then half 

 that of air at the level of the sea). But when in movement it 

 became difficult to enlarge the breathing capacity to the extent 

 necessary to meet the further demand for air which was the 

 result of muscular exertion ; ^ and, notwithstanding the increased 

 efforts which were put forth to meet this demand, there was, in 

 all probability, a considerable deficiency in the weight and value of 

 the amount which was imbibed. 



When the effects consequent upon experiencing diminution in 

 atmospheric pressure were first noticed, it was guessed that they 

 were in some way due to a peculiarity in the air. Father Joseph 

 de Acosta was amongst the earliest to mention the subject, and in 

 Book III of his Natural & Moral History he devotes a Chapter 

 to ^^ Some mervellous effects of the windes, which are in some 

 partes of the Indies, ^^ giving first a few prefatory remarks upon 

 sea - sickness, which he says ^^it be true that the motion of the 

 shippe helpes much, in that it moves more or less, and like- 

 wise the infections and ill - savours of things in the shippe ; 

 yet the proper and naturall cause is the aire and the vapors 

 of the sea. . . It is proved by many experiences, that the aire 

 of the sea is the chief e cause of this strange indisposition '' ; 

 and, having settled to his own satisfaction that the air of the 



The immunity from headache of Mr. Perring and others who accompanied us 

 I consider was due to their having lived for a considerable length of time at lower 

 pressures than ourselves. 



^ In ascending a mountain, the respiration is quickened by two causes— (1) by 

 muscular exertion, and (2) by diminution in pressure. These act independently of 

 each other. 



