RESPIRATORY EXCHANGE IN WATER. 699 



structed upon these principles are those used by Zuntz, 1 Geppert 2 and 

 Lowy. 3 A diagram of such an apparatus is shown in Fig. 66. 



The disadvantage of these methods is that, owing to the attention 

 of the subject being directed to the breathing, the volume of air 

 respired during a limited period is not a fair sample upon which to 

 base an exact calculation, and, moreover, the depth and the rate of 

 breathing are also liable to another source of disturbance, the resistance 

 of the apparatus. For these and other reasons, 4 the results obtained 

 during short periods of observation are liable to lead to erroneous 

 conclusions. 



Methods similar to those just mentioned have been employed in the 

 case of animals, 5 the mouth and nose being covered with a respiration 

 mask or the trachea connected by a cannula with the apparatus 

 necessary for the measurement of the inspired and expired air. It is 

 obvious that these methods introduce many sources of disturbance ; the 

 animals, unless horses be used, must be tied down, and in many cases 

 anaesthetised, conditions which markedly affect the respiratory exchange. 6 

 For these reasons the methods of Pettenkofer and Haldane are in most 

 cases to be preferred, for the animals are placed under conditions as 

 far as possible normal ; these methods are, however, unsuitable when 

 operative procedures have to be carried on at the same time as the 

 determination of the respiratory exchange. 



Methods for the measurement of respiratory exchange in water. 



The respiration of fishes was studied by Humboldt and Provenal 7 in the follow- 

 ing manner : The fishes were placed in a flask of water, the gaseous contents 

 of which had been analysed, and then after an interval a sample of the water 

 was examined and the alteration in its gases determined. The quantity of 

 water present was measured, and thus it was possible to estimate the amount 

 of gases absorbed and discharged by the fish. A similar method has been 

 used by Yernon 8 for the measurement of the respiratory exchange in marine 

 invertebrates. 



Baumert 9 improved this method by passing a stream of water through the 

 flask containing the animals ; the gases contained in a sample of the water 

 entering and in the water leaving the flask were determined. A modification 

 of Regnault and Reiset's method was introduced by Jolyet and Keynard; 10 

 a stream of air was made to bubble slowly through the water in which the 



1 JBerL klin. Wchnschr., 1887, S. 429 ; Arch. f. Physiol., Leipzig, 1889, S. 166. 

 ' 2 Arch.f. exper. Path. u. Pharmakol., Leipzig, 1887, Bd. xxii. S. 368. 

 >>Arch.f. d. ges. Physiol., Bonn, 1888, Bd. xlii. S. 268; ibid., 1888, Bd. xliii. S. 519; 

 ibid., 1891, Bd. xlix. S. 492. 



4 See p. 754. 



5 Sczelkow, Sifzungsb. d. k. AJcad. d. Wissensch. Math.-natunv. Cl., Wien, 1862, 

 Bd. xlv ; Kowalewsky, Ber. d. k. scich*. Gesellsch. d. Wissensch. Math.-phys. KL, 1866, 

 Bd. xviii. S. Ill ; Sanders-Ezn, ibid., 1867, Bd. xix. S. 58 ; Arb. a. d. physiol. Anst. zu 

 Leipzig, 1868, S. 58 ; Scheremetjewski, Bcr. d. k. sdchs. Gesellsch. d. Wissensch. Math.- 

 phys. KL, 1868, Bd. xx. S. 154 ; Robrig and Zuntz, Arch. f. d. gcs. Physiol., Bonn, 

 1871, Bd. iv. S. 57 ; Zuntz, ibid., 1876, Bd. xii. S. 522; Finkler and Oertmann, ibid., 

 1877, Bd. xiv. S. 38; Pfliiger, ibid., 1878, Bd. xviii. S. 247; Haniiot and Ricliet, 

 Compt. rend. Soc. de biol., Paris, 1886 ; Compt. rend. Acad. d. sc., Paris, 1887, tome civ. 

 p. 435; Fredericq, Hen. scient., Paris, 1880 ; Bull. Acad. roy. d. sc. de Belg., Bruxelles, 

 1886. 



6 See p. 717. See also "Animal Heat," this Text-book, vol. i. 



7 Mem. de, la Soc. de phys. et de chim. d'Arcueil, Paris, 1807, tome ii. p. 359 ; Journ. 

 f. Chem. u. Phys., Niirnberg, Bd. i. S. 86. 



8 Journ. Physiol., Cambridge and London, 1895-96, vol. xix. p. 18. 



9 "Chem. Untersuch. u. d. Respir. d. Schlammpeitzgers," Breslan, 1855, S. 24. 

 10 Arch, de physiol. norm, etpoth., Paris, 1877, tome iv. p. 44. 



