7 3 6 CHEMISTR Y OF RESPIRA TION. 
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, Phi!. Trans.. Loudon, 1808, pp. 266 and 2S0 ; 1809, pp. 415 and 
427; Paul Bert, "La pression barom&rique," 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. J. sc, Paris, 1789, p. 566 ; Regnaultand Reiset, 
Aim. de cJiiin. ctphys., Paris, 1849, Ser. 3, tonic xxvi. ; Dohmeii, " 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., Strassbnrg, 
1883-84, Bd. viii. S. 313; Arch.f. Physiol., Leipzig, 1884, S. 308. See also references 
given by Phillips, loc. tit. supra. 
3 Ransome, Med. Chron., Manchester, April 1888, May 18S9 ; 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 pharmacologic, 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 Paid Bert. "La pression barometrique," Paris, 1878, p. 800. See also Lehmann, 
Arch. f. d. ges. Physiol, Bonn, 1S84, Bd. xxxiii. S. 173; Liebig, Arch. f. Phi/siol, 
Leipzig, 1SS9, Supp. Bd. S. 41; A. H. Smith, "The Effects of High Atmospheric 
Pressure, including the Caisson Disease," Brooklyn, 1873 ; Philippon, Joum. de Vaunt, d 
physiol. etc., Paris, 1894, tome xxx. pp. 296, 414. 
