RESPIRA TOR Y EXCHANGE IN 1 1 'A TER. 699 
Btructed upon these principles are those used by Zuntz, 1 Geppert 2 and 
Lowy. 3 A diagram of such an apparatus is Bhown 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 ohtained 
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 clown, and in many cases 
amesthetised, 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 
deterarination of the respiratory exchange. 
Methods for the measurement of respiratory exchange in water.— 
The respiration of fishes was studied by Humboldt and Provencal " in the follow- 
ing manner : — The fishes were placed in a flask of water, the gaseous content> 
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 Vernon s 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 hi the water leaving the flask were determined. A modification 
of Regnault and Eeiset's method was introduced by Jolyet and Reynard ; 10 
a stream of air was made to bubble slowly through the water in which the 
1 Berl. Hin. Wchnschr., 1887, S. 429 ; Arch. f. Physiol., Leipzig, 1889, S. 160. 
- Arch. f. exper. Path. u. Pharmakol., Leipzig, 1887, Bd. xxii. S. 368. 
3 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. 
3 Sczelkow, Sitzungsb. d. k. Akad. d. Wissensch. Mabh.-naturw. CI., Wien, 1862, 
Bd. xlv ; Kowalewsky, Be/: d. k. srichs. Gesellsch. d. Wissensch. Math.-phys. Kl., 1866, 
Bd. xviii. S. Ill ; Sanders-Ezn, ibid., 1867, Bd. xix. S. 58 ; Arb. ». d. physiol. Anst. :>' 
Leipzig, 1868, S. 58; Seheremetjewski, Per. d. k. sdchs. Gesellsch. d. Wissensch. Math.- 
phys. Kl., 1868, Bd. xx. S. 154; Rohrig and Zuntz, Arch. f. d. ges. 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; Hanriot and Richet, 
Compt. rend. Soc. de biol., Paris, 18S6 ; G'ompt. rend. Acad. d. sc, Paris, 1887, tome civ. 
p. 435 ; Fredericq, fiev. 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. 
''Mem. de. la Soc. de phys. et de chivi. d'Arcueil, Paris, 1807, tome ii. p. 359; Journ. 
f. Chem. u. Phys., X/iirnberg, Bd. i. S. 86. 
* Jouni. Physiol., Cambridge and London, 1895-96, vol. xix. p. 18. 
9 " Chem. Untersuch. u. d. Respir. d. Schlammpeitzgers, " Breslau, 1855, S. 24. 
10 Arch, de physiol. norm, etpath., Paris, 1877, tome iv. p. 44. 
