Theories and Experiments 217 



duces in a very rare air an acceleration in respiration and circulation, 

 from which there results distress which is unendurable to certain tem- 

 peraments. (Vol. I, p. 207-209.) 



But the first interpretation accepted by de Saussure, the de- 

 crease of the weight sustained, had success much above its deserts, 

 whereas the second, which contains, as we shall see, a part of the 

 truth, remained much less widely known. 



Some years after him, the physiologist 25 Fodere underlined his 

 mistake, so to speak, comparing the hemorrhages from decreased 

 pressure to those which follow the application of cupping-glasses: 



The atmospheric pressure keeps the vessels from being too forcibly 

 distended by the liquids which they contain and by the elastic force 

 of the air abundant there ... If this pressure is removed, or if its 

 intensity is merely lessened, the parts undergo considerable swelling 

 and hemorrhages; we have common examples of it ... in suction, in 

 the operation of cupping-glasses, in the hemorrhages of travellers who 

 ascend to the summits of lofty mountains; in the heaviness, distention 

 and discomfort which we experience whenever the air is lighter. (P. 

 220.) 



Halle and Nysten 2r> share this opinion and express it with the 

 greatest clearness. For them, in the first place, the chief effect is 

 due to the removal of the weight of the atmosphere: 



Whenever one places an animal under the receiver of the pneu- 

 matic machine, or when one mounts rapidly to considerable heights, 

 then not only the sudden expansion of the free elastic fluids, propor- 

 tional to the rapid decrease of the atmospheric pressure, but also 

 the tendency to expansion which exists in the animal liquids them- 

 selves, especially in the elastic fluids which they hold in solution, may 

 be the cause of several striking results, such as a feeling of general 

 discomfort, etc. 



However, after describing the phenomena presented by travel- 

 lers and balloonists, the authors seem to relegate their entirely 

 mechanical explanation to a secondary place, for they add: 



These effects are easily accounted for. On account of the decrease 

 in the density of the air there is a lessened quantity in the same 

 volume. This air, therefore, is less adequate for the combinations which 

 it must experience in the act of respiration; consequently, so that in 

 rarefied air these combinations may take place conformably to the 

 purpose of nature, one must breathe proportionately with greater 

 rapidity. This is the cause of this hasty and panting respiration and 

 consequently of the acceleration of the pulse rate which results from 

 it. We even comprehend that at much greater heights the rarefaction 

 of the air would be such that acceleration of the respiration would 



