7° PRINCIPLES OF ANIMAL NUTRITION. 
data, with the addition of analyses of the known volume of air 
contained in the apparatus at the beginning and end of the 
experiment, afford the means of computing both the carbon dioxide 
and other gases given off and the oxygen cousumed.* 
In theory this is the most complete and satisfactory type of 
respiration apparatus, since it permiis a determination of the total 
gaseous exchange. Serious practical difficulties have been found 
in its use, however, especially for the larger animals, among them 
the difficulty of maintaining the air reasonably pure, the difficulty 
of securing a uniform temperature and mixture of the gases in a 
large and complicated apparatus, and the liability to contamination 
of the oxygen used. Seegen & Nowak ft used an apparatus of 
this type for their experiments upon the excretion of gaseous nitro- 
gen by animals (see p. 42). Laulanié { has described a Regnault 
apparatus for small animals in which a continuous graphic measure- 
inent of the oxygen admitted to the apparatus is made, Hoppe- 
Seyler § has constructed at Strasburg an apparatus of this type 
large enough to contain a man, and Bleibtreu || has recently made 
use of a small one to investigate the formation of fat in geese, but 
the apparatus has not come into general use.{ 
The Pettenkofer Apparatus.—The second type of respiration 
apparatus is that of v. Pettenkofer. In this type the subject 
breathes in a closed chamber through which a measured current 
of air is maintained. 
Scharling ** appears to have been the first to construct an appa- 
ratus of this sort. The ingoing air was freed from carbon dioxide 
by passing through potash solution, while the outcoming air, after 
drying, gave up its carbon dioxide to a weighed potash bulb. Vari- 
ous similar forms of apparatus were constructed, but it was found 
*For a description of the apparatus, see also Hoppe-Seyler, Physiol. 
Chem., pp. 526 and 536. 
{Sitzungsber. Wiener Akad., Math.-Naturwiss. Classe, 71, III, 329; 
Arch. ges. Physiol., 19, 349. 
f Archives de Physiol., 1890, p. 571. 
§ Zeit. physiol. Chem., 19, 574. 
|| Arch. ges. Physiol., 85, 366. 
[See also Pfliger and Colasanti (Arch. ges. Physiol., 14, 92) and Schulz 
Ub., p. 78). 
** Ann. Chem. Pharm., 45, 214. 
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