CHEMICAL PHENOMENA OF RESPIRATION. 329 



considerable muscular force. These different symptoms, 

 especially the lowering of the temperature, appear, however, 

 to come from another cause, which can only be explained 

 by means of the knowledge recently acquired as to the 

 -mechanical equivalent of heat (see p. 79). L. Lortet, who 

 has studied the mountain sickness 1 (mal des montagnes), 

 by the aid of almost every registering instrument now 

 employed in physiology (the sphygmograph, the anapno- 

 graph, special thermometers, etc.), attributes the cooling of 

 the body to the fact that the internal combustion is unable to 

 maintain the previous temperature, which has to contend at 

 once against the external cold, and tjie loss of the heat which 

 is being transformed into muscular effort : in short, the in- 

 tensity of the respiratory combustion increases in proportion 

 to the force expended (Gavarret) ; heat is transformed into 

 mechanical force, sufficient heat being formed for this pur- 

 pose, in accordance with the density of the air and the 

 quantity of oxygen inhaled. " In ascending mountains, how- 

 ever, and especially when at a great height, and on declivities, 

 where the labor of ascent is very great, an enormous quantity 

 of heat is required to be transformed into muscular force. 

 This expense of force consumes more heat than the organism 

 can furnish; consequently the body grows sensibly colder, 

 rendering frequent halts necessary, for the purpose of recov- 

 ering warmth. During the process of digestion chill is 

 scarcely perceptible : consequently the guides advise trav- 

 ellers to take food once in every two hours, or thereabouts." 



These facts serve to explain the effect produced on the 

 health and pathology of the inhabitants of high mountains, 

 caused by the feeble pressure of the atmosphere in which 

 they live. These men, as has been shown by Jourdanet, 

 exist in an atmosphere containing an insufficient quantity of 

 oxygen : they are anoxy hematics}- 



2. If an animal be shut up in a confined space, and a suffi- 

 cient quantity of oxygen be admitted, while the carbonic acid 

 produced by respiration is allowed to accumulate, the animal 

 will die, as soon as the proportion of this gas becomes too 

 great; the time needed to produce this effect differs greatly 



1 L. Lortet, " Deux Ascensions au Mont- Blanc en 1869, Re- 

 cherches Physiologiques sur le Mal des Montagnes." Paris, 

 Victor Masson, 1809; and "Revue des Cours Scientifiques. " 

 1809-70. 



1 Jourdanet, " Le Mexique et 1'Amerique Tropicale." Paris. 

 1804. 



