742 CHEMISTR Y OF RESPIRA TION. 



that the " noxious vapours " produced by repeatedly breathing the same 

 air could be removed by potash, and the air rendered fit for respira- 

 tion. A few years later, Black l showed that the " noxious vapours " 

 were carbon dioxide. 



The importance of the several factors mentioned above has been differ- 

 ently estimated by various observers. 2 Brown-Sequard and d'Arsonval 3 

 concluded that volatile poisons were given off from the lungs of healthy 

 men and animals, for they found that the condensed vapour of breath 

 caused death when injected into rabbits ; that rabbits made to breathe 

 air vitiated by the respiration of other rabbits until the carbon dioxide 

 was 2 to 6 per cent., died, unless the supposed volatile poisons were 

 removed by previously passing the aif over pumice soaked in sulphuric 

 acid; that no bad effects were produced when men breathed for an 

 hour or two air containing 20 per cent, of pure carbon dioxide. 

 The experiment of injecting the condensed vapour of breath has been 

 repeated by Dastre and Loye, 4 Hoffmann- Wellenhof, 5 Lipari and Crisa- 

 fulli, 6 and Lehmann and Jessen, 7 but the results were negative. 



Eichardson 8 maintained that breathed air was poisonous, even though 

 all the carbon dioxide and other impurities had been removed ; the cause 

 he considered to be " devitalised oxygen," whatever that term may mean. 

 Jackson 9 thought that carbon monoxide was the poison. From experi- 

 ments performed upon himself, Angus Smith 10 concluded that air vitiated 

 by respiration until it contained 1 per cent, carbon dioxide, produced 

 distinct feelings of discomfort. 



Experiments, however, performed by Hermans n have shown that 

 no volatile poisons are given off by respiration, and more recently 

 Haldane and Lorrain Smith, 12 in an investigation of the subject, both 

 as regards animals and men, have confirmed and extended Hermans' 

 work. The following are the chief conclusions given by Haldane and 

 Lorrain Smith : 



" 1. The immediate dangers from breathing air highly vitiated by 

 respiration arise entirely from the 'excess of carbon dioxide and 

 deficiency of oxygen, and not from any special poison. 



" 2. The hyperpncea is due to excess of carbon dioxide, and is not 

 appreciably affected by the corresponding deficiency of oxygen. The 

 hyperpnrea begins to appear when the carbon dioxide rises to from 

 3 to 4 per cent. At about 10 per cent, there is extreme distress. 



" 3. Excess of carbon dioxide is likewise the cause, or at least one 

 cause, of the frontal headache produced by highly vitiated air. 



" 4. Hyperpnoea from defect of oxygen begins to be appreciable when 

 the oxygen in the air breathed has fallen to a point which seems to 



1 "Lectures on Chemistry," ed. Robison, Edinburgh, 1803. 



2 See Merkel, Arch. f. Hyg., Miinchen u. Leipzig, 1892, Bd. xv. S. 1, where further 

 references are given. 



3 Compt. rend. Acad. d. sc., Paris, 1888, tome cvi. pp. 106, 165 ; Comyt. rend. Soc. de 

 bioL, Paris, 1887, p. 814 ; 1888, pp. 33, 90, 99, 151. 



4 Ibid., 1888, pp. 43 and 91. 



5 Wien. klin. Wchnschr., December 13, 1888. 



6 Butt. gen. de therap. etc., Paris, 1889, No. 46, p. 524. 



7 Arch.f. Hyg., Miinchen u. Leipzig, 1890, Bd. x. S. 367. 



8 Brit. Med. Journ., London, 1860, vol. ii. ; Chem. News, London, vol. Iv. p. 253. 



9 "Proc. Physiol. Soc.," December, 1887, in Journ. PhysioL, Cambridge and London, 

 vol. ix. 



10 "Air and Rain," p. 130. 



11 Arch.f. Hyg., Miinchen u. Leipzig, 1883, Bd. i. 



12 Journ. Path, and Bacterial., Edin. and London, 1892, vol. i. p. 175. 



