APPENDIX. EXPERIMENTS BY M. PAUL BERT. 437 



J.— EXPERIMENTS BY M. PAUL BERT. 



The book entitled La Pressioti Barometrique, by Mons. P. Bert, was pub- 

 lished in 1878, but I refrained from reading or procuring it until after my 

 return from Ecuador. It did not appear to me likely that the points which 

 1 desired to investigate could be settled by laboratory experiments, and this 

 seems also to have been the opinion of M, Bert.^ 



The general conclusions which are given at the close of the book (pp. 

 1153-55) in respect to the effects of diminished pressure ^ are : — 



1. La diminution de la pression barometrique n'agit sur les etres vivants qu'en 

 diminnant la tension de Foxygene dans Pair qu'ils respirent, dans le sang qui anime 

 leurs tissus, et en les exposant ainsi a des menaces d'asphyxie (p. 1153). 



2. Les effets fa 'heux de la diminution de pression peuvent etre efficacement combattus 

 par la respiration d''un air suffisamment riche en oxygene pour maintenir a la valeur normale 

 la tension de ce gaz (p. ^154). 



3. Les etres actuellement existants a Tetat sauvage sur la surface du globe sont 

 accommodes au degre de tension oxygenee sous laquelle ils vivent : toute diminution, 

 toute augmentation parait leur etre defavorable quand ils sont ddns Tetat de sante (p. 

 1155). 



These conclusions were arrived at after a very long series of experiments 

 of various kinds had been made upon birds, dogs, cats, rabbits, etc., from 

 which it clearly appeared that death can be brought about in these animals 

 if pressure is reduced rapidly to a low point. Sparrows, for example, were 

 killed before pressure had been reduced so low as that which reigns at the 

 summit of Mount Everest. Dogs, it was found, were harder to kill than cats 

 (p. 738). The various animals exhibited much the same symptoms at these 

 artificially produced low pressures as human beings at the natural low pressures 

 which are experienced at great heights ; and, like them, they recovered very 

 rapidly (even when apparently dying) when pressure was restored. 



In further experiments with sparrows, pressure was lowered very rapidly, 

 and the birds operated upon were reduced to a dying state ; oxygen was then 

 let in, and the birds revived ; pressure was then still further reduced and the 

 birds were again made extremely ill,' but recovered by a further introduction 

 of oxygen ; and the experiments were continued until the atmosphere in 

 which the birds were confined contained 91 per cent of oxygen, and in that 

 mixture they lived at a pressure of 75 millimetres, which is less than a third 



1 He says in his Preface, "j'ai dfl laisser systematiquement de c6te trois ordres de 

 questions qui ne pouvaient etre attaquees dans le laboratoire, et pour lesquelles, par suite, 

 les conditions certaines de la preuve ne pouvaient etre rassemblees ; c'est a savoir : les 

 oscillations quotidiennes du barometre, les applications therapeutiques, V acdimatement 

 sur les hauls Heux.'''' 



2 Numerous experiments at augmented pressures were also made. 



