R ESPIRA TOR V CHANGES IN AIR. 695 
The cjirlinii dioxide is ahsurhed from the air hy caustic potash, and a 
constant supply of oxygen from the reservoirs is driven in, a manometer 
in communication with the animal chamber indicating the prassure. 
Samples of air for analysis can he drawn from the chamber, and thus 
the part played hy nitrogen determined, and a control placed upon the 
completeness of the supply of oxygen and the removal of carbon 
dioxide. Modified forms of Eegnault and Reiset's apparatus have been 
used by Hoppe-Seyler and Stroganow, 1 Pfliiger and Colasanti, 2 Sehulz, 3 
Seegen and Nowak. 4 
In Scharling's 5 respiration apparatus a constant stream of fresh air 
was drawn through the chamber in which the animal was confined. A big 
barrel served for the chamber, and air freed from carbon dioxide by 
passing through Liebig's potash bulbs was aspirated through the appar- 
atus : on leaving the chamber the air passed through a flask containing 
sulphuric acid, which removed the moisture, and through a weighed 
potash bulb of huge size, of which the increase in weight gave the 
amount of carbon dioxide expired by the animal. As a control, a sample 
of air for analysis was removed from the barrel at the beginning and 
end of the experiment. In this method the carbon dioxide alone was 
determined, and the results were inaccurate, for the absorption was 
incomplete, as is shown hy the fact that the air leaving the bulbs 
rendered lime water turbid. Many other forms of apparatus constructed 
upon similar principles have been used. 6 
With the methods formerly in use it was impossible to maintain a 
steady ventilation, and at the same time completely absorb the carbon 
dioxide. To Overcome this difficulty, Pettenki >fer " introduced the 
following modification. The total amount of air drawn through the 
apparatus is measured by a meter : continuous samples of the air 
entering and leaving the chamber are steadily drawn through two 
separate systems of absorption tubes and meters for the determination 
of the moisture, carbon dioxide, and volume of the samples. The 
difference in the amounts of water and carbon dioxide contained in the 
two samples, multiplied by the total ventilation, gives the quantity of 
moisture and carbon dioxide discharged by the animal. The intake 
of oxygen is estimated in the following way. The animal is weighed at 
the beginning and at the end of the experiment, and the difference 
between the weights of carbon dioxide and water discharged, and the loss 
in weight of the animal, represents the oxygen absorbed. Thus if "NV 
represents the initial weight of the animal, and W, its final weight, then 
W - W t z=w, the loss in weight of the animal. Let C0 2 + H. 2 represent 
the weights of carbon dioxide and water discharged during the experi- 
ment, then C0 2 + H 2 — v:=0. 2 , the oxygen absorbed. In thus estimat- 
ing the oxygen, it is assumed that, apart from the carbon dioxide and 
1 Arch. f. d. ges. Physiol., Bonn, 1876, Bd. xii. S. 18. 
- Ibid., 1877, Bd. xiv. S. 92. 
-Ibid., Bd. xiv. S. 78. 
* Ibid., 1879, Bd. xix. S. 347. 
5 Ann. d. Chem. u. Pharm., 1843, Bd. xiv. S. 214. 
6 Allen and Pepys, Phil. Trans., London, 1809, pt. 2, p. 412; Dnlong, Ann. dechim. 
et phys., Paris. 1841, Ser. 3, tome i. p. 440; Despretz, ibid., 1824, tome xxvi. p. 337 : 
Boussingault, ibid., 1844, Ser. 3, tome xi. p. 433 ; Journ. f. prakt. Chem., Leipzig, 1845, 
Bd. xxxv. S. 402 ; Senator, Arch. f. Anat., Physiol, u. xcissensch. Med., 1872, S. 1 : Lieber- 
meister, Deutsches Arch. f. klin. Med., Leipzig, 1870, Bd. vii. S. 75. 
7 Sitzungsb. d. k.-bayer. Akad. d. JJ'issensrh. zu Munchen, math. -phys. CI., 1862, Bd. 
ix. (2), S. 232 ; Ann. d. Chem. u. Pharm., 1862-63, Supp. Bd. ii. S. 17. 
