344 



RESPIRATION. 



several of the calculations of the amount 

 of the watery vapour exhaled from the 

 lungs proceed on the supposition that the 

 expired air is saturated with moisture, but 

 this has not been substantiated by the only 

 experiments made with the view of deter- 

 mining this point. In Moleschott's experi- 

 ments, the amount of water held in solution 

 varied. In five out of seven experiments the 

 watery vapour in the expired air was appre- 

 ciably less than what is sufficient to saturate 

 air of the same temperature, while in one 

 experiment it was saturated. On taking the 

 average difference in the seven experiments 

 performed, as much as possible under similar 

 circumstances, between the actual quantity of 

 moisture in the expired air, and in air of the 

 same temperature saturated with moisture, he 

 found that 2420 cub. cent. ( 147*620 Eng. 

 cub. inches) of the expired air would require 

 a quantity of watery vapour additional to that 

 already existing in it equal to lOmillegrammes 

 ('150 Eng. Troy grains) to saturate it. From 

 these experiments he concludes " that in the 

 greater number of instances the expired air 

 in man is not saturated with watery vapour, 

 but sometimes such a saturation occurs."* 

 Magendie observed, in experiments on dogs, 

 that the escape of an increased quantity of 

 watery vapour from the mouth follows the 

 injection of water into the veins, caused, as 

 he supposes, by the transpiration from the 

 lungs being considerably increased.-]" 



Animal matters in quantities too minute 

 to be subjected to analysis are also exhaled 

 from the lungs, and escape along with the 

 expired vapour. The condensed vapour 

 from the lungs, when collected in a vessel, 

 and kept for some days, putrefies, and 

 emits an ammoniacal smell. J We are also 

 often sensible of the escape of different 

 substances, previously taken into the sto- 

 mach, along with the expired air, by their 

 smell ; and the experiments of Nysten , 



of air respired by himself in a state of rest, supposing 

 the temperature of the expired air to be 98-6 Fahr., 

 and saturated with moisture, the temperature of the 

 inspired air to be 57'2 F., and containing only its 

 average quantity of moisture, that the quantity of 

 water in the expired air will amount in the 24 hours 

 to 5555-880 Troy grains, of which, on an average, 

 4953'993 grains may he allowed for the loss of water 

 from the inner surface of the lungs and air passages, 

 and 601-887 grains for the quantity previously con- 

 tained in the inspired air. As, however, the body is 

 not at rest during a considerable part of the 24 hours, 

 the loss of watery vapour must be greater than this. 



* Hollandisclie Beitrage zu den anatomischen 

 und physiologischen Wissenschaften, band i. S. 96. 

 1846. " 



f Compendium of Physiology, translated by Mil- 

 ligan, p.395. 1831. 



J Valentin and Brunner (Opus cit. pp. 571, 572), 

 in their experiments on the human species, detected 

 the presence of a minute quantity of organic matter 

 in the expired air. This was ascertained by the 

 sulphuric acid, through which the expired air was 

 made to pass, becoming red. Marchand (Journal 

 fur praktische Chemie, von Erdman und Marchand, 

 band xxxiii. S. 129. 1844), in his experiments on 

 frogs, also observed this. 



Recherches de Physiologic, &c. p. 145. 



Magendie*, Tiedemannf, and others, prove 

 that various organic and mineral substances, 

 when injected into the veins, escape in part 

 by exhalation from the lungs. 



If the inspired air, during its sojourn in the 

 lungs, becomes increased in bulk from an 

 increase in temperature and an addition of 

 watery vapour, it suffers a small diminution 

 from the absorption of part of its constituent 

 gases. The older experimenters observed a 

 diminution in the air respired, but as they 

 experimented with imperfect apparatus, and 

 transmitted the expired air through water 

 which would absorb part of the carbonic acid 

 gas, little confidence is to be placed in their 

 results. J There can be no doubt that a 

 greater amount of oxygen disappears from 

 the inspired air than what is sufficient for the 

 formation of the quantity of carbonic acid 

 gas in the expired air, and that there is a 

 slight diminution in the bulk of the expired 

 air from this cause ; but we cannot speak so 

 decidedly regarding any changes in the quan- 

 tity of the nitrogen. Provencal and Hum- 

 boldt, in their experiments on the respi- 

 ration of fishes, and Spallanzani [|, in his 

 experiments on snails, observed an absorption 

 of azote : while JurineH and Nysten**, in their 

 experiments on the human species, and Ber- 

 tholletft, DespretzJJ, Dulong, and Mar- 

 tigny || || , in their experiments on warm-blooded 

 animals, and TreviranusfH in his experiments 

 on the cold-blooded animals, observed an 

 exhalation of azote. Dr. W. F. Edwards * * *, in 



* Opus cit. 



t Zeitschrift fur Physiologie, hand v. 1835. This 

 paper is translated in the British and Foreign Quar- 

 terly Review, vol. i. p. 241. Tiedemann, in this 

 paper, has given an account of all the experiments 

 previously performed on this point by others. 



J Goodwyn (Opus cit. p. 51), Plaff (Nicholson's 

 Journal of Natural Philosophy, vol. xii. p>. 249. 

 1805), Dr. Alex. Henderson (Nicholson's Journal, 

 vol. viii. p. 40), and Sir H. Davy (opus cit.), in their 

 experiments on the human species, observed a dimi- 

 nution in variable proportions in the respired air ; 

 and Henderson, Plaff, and Davy, supposed that part 

 of this diminution was caused by the absorption of 

 nitrogen at the lungs. 



Mem. de la Societe d'Arcueil, 'torn. ii. p. 388. 

 1809. 



|| Memoire sur la Respiration, traduit par Sene- 

 bier, pp. 162, 184, and 230. 1803. An absorption of 

 azote was not uniformly observed by Spallanzani. 



^[ Memoire couronne en 1787, par la Societe 

 Royale de Medecine, as quoted by Nysten. 



** Opus cit. p. 186. 



ff Mem. de la Socie'te d'Arcueil, torn. ii. p. 459. 



j j Annales de Chimie et de Physique, torn. xxvi. 

 p. 337, 1824.' 



Magendie's Journal de Physiologie, torn. iii. 

 p. 45. 1823. 



Jill Magendie's Journal, torn. x. p. 337. 1824. 



^[^[ Zeitschrift fiir Physiologie, hand iv. Trevi- 

 ranus says, " in some of my experiments there was 

 more azote than carbonic acid exhaled, and this not 

 only in the avertebrata, but also in the frog." p. 33. 



*** De 1'Influence des Agens Physiques sur la Vie, 

 p. 420. Tableaux 63, 64, and 65. 1824. Dr. Edwards 

 concludes from his experiments that there is both a 

 constant exhalation and absorption of azote at the 

 lungs, and that these two actions are sometimes 

 equal, while at other times the one preponderates 

 over the other. 



