736 CHEMISTR Y OF RESPIRATION. 



cases irritant effects, probably due to the presence of impurities in the 

 gas, were noticed. 



Considerable discussion has arisen concerning the effect of an in- 

 creased percentage of oxygen in the air breathed upon the respiratory 

 exchange. Is there or is there not an increase in the absorption of 

 oxygen and the discharge of carbon dioxide under these conditions ? 

 Many observers l maintain that there is a distinct augmentation of the 

 metabolism of the body, others 2 find that the respiratory exchange of a 

 normal animal is the same in amount, whether it breathes air or pure 

 oxygen. Without entering into a discussion of the numerous con- 

 tradictory answers to this question, it is permissible to draw the 

 following conclusions : The normal animal does not increase its 

 respiratory exchange when it breathes oxygen instead of air, for its 

 metabolism is regulated by the needs of its tissues, and not directly 

 by the amount of oxygen absorbed in the lungs ; in the case of some 

 diseases, during which the blood, owing to diminished absorption of 

 oxygen in the lungs, is abnormally venous, the breathing pure oxygen 

 would increase the percentage of oxygen in the alveolar air, and thus 

 enable the blood in the lungs to take up more oxygen. In these cases 

 breathing oxygen under pressure greater than that of the oxygen in 

 the air would, for a similar reason, be effective, and would also in- 

 crease the amount of oxygen simply dissolved in the plasma. It 

 would appear, therefore, that there is strictly no contradiction in 

 most of the experimental and clinical results, for in the normal 

 animal breathing ordinary air the arterial blood is almost .saturated 

 with oxygen, and without doubt contains as much or more oxygen 

 than the tissues need. This is certainly not the case in some dis- 

 eases, during which the patients have derived benefit from breathing 

 oxygen. 3 



In connection with the respiration of pure oxygen or of air, Paul 

 Bert 4 made the important discovery that animals exposed to a pressure 

 of oxygen above six atmospheres died in violent convulsions. This 

 result is not due to the purely physical effects of the increased pressure, 

 but to the augmentation in the tension of oxygen, for if the experiment 

 be made with air, a greater and greater pressure can be borne, until 



1 Allen and Pepys, Phil. Trans., London, 1808, pp. 266 and 280; 1809, pp. 415 and 

 427; Paul Bert, "La pression barome'triqne," Paris, 1878, p. 832. Further references are 

 given by Phillips, "Materia Medica, Pharmacology, and Therapeutics Inorganic Sub- 

 stances," London, 1894, 2nd edition, p. 2. 



2 Lavoisier and Sequin, Hist. Acad. roy. d. sc., Paris, 1789, p. 566 ; Regnault and Reiset, 

 Ann. de chim. ctphys., Paris, 1849, Ser. 3, tome xxvi. ; Dohnien, " Arb. d. Bonner physiol. 

 Inst.," 1865 ; Speck, Arch. f. d. ges. Physiol., Bonn, 1879, Bd. xix. S. 171 ; Kempner, 

 Arch. f. Physiol., Leipzig, 1884, S. 396; Lukjanow. Ztschr. f. physiol. Chem., Strassburg, 

 1883-84, Bd. viii. S. 313 ; Arch. f. Physiol., Leipzig, 1884, S. 308. See also references 

 given by Phillips, loc. cit. supra. 



3 Ransome, Med. Chron., Manchester, April 1888, May 1889 ; A. H. Smith, "Oxygen 

 Gas as a Remedy in Disease," New York, 1870, 2nd edition ; W. G. Thompson, Practi- 

 tioner, London, 1889, vol. xliii. p. 97. At the end of this article is a list of thirty-two 

 papers on the subject. See also article "Oxygene" in " Dictionnaire de therapeutique, de 

 matiere medicale, de pharmacologie, de toxicologie et des eaux minerales, " par Dujardin- 

 Beaumetz, Paris, 1889, tome iv. p. 101. See also Phillips, loc. cit. supra, and references 

 there given. 



4 Paul Bert, "La pression barometrique, " Paris, 1878, p. 800. See also Lehmann, 

 Arch. f. d. ges. Physiol., Bonn, 1884, Bd. xxxiii. S. 173 ; Liebig, Arch. f. Physiol., 

 Leipzig, 1889, Supp. Bd. S. 41; A. H. Smith, "The Effects of High Atmospheric 

 Pressure, including the Caisson Disease," Brooklyn, 1873 ; Philippon, Journ. de Tanat. et 

 'I. etc., Paris, 1894, tome xxx. pp. 296, 414. 



