212 NUTRITION OF FARM ANIMALS 



If the entire respiratory exchange is to be determined, the 

 subject is placed in the respiration chamber represented in the 

 diagram. If only the pulmonary exchange is under investi- 

 gation, the respiration chamber is replaced by a mask or mouth- 

 piece or even by a suitable cannula inserted in the trachea. 



The original form of the Regnault-Reiset apparatus l is shown in 

 Fig. 25. The same investigators subsequently devised a larger one 

 in which they made a number of experiments upon animals of various 

 species including sheep, calves, swine and fowls. In theory this is 

 the most perfect form of respiration apparatus, but numerous tech- 

 nical difficulties arise in its use. Various later forms have been de- 

 vised but At water and Benedict 2 were the first to construct one of a 

 size suitable for man which was capable of a high degree of accuracy. 

 Quite recently Zuntz 3 has constructed a respiration apparatus of 

 this type for experiments on domestic animals, a section of which 

 is shown in Fig. 26, while for the determination of the pulmonary 

 exchange, Benedict 4 has devised a so-called " Universal " respiration 

 apparatus. 



299. The Pettenkofer apparatus. In the Pettenkofer, or 

 open circuit, respiration apparatus, the subject breathes in a 

 continuous measured current of atmospheric air whose content 

 of water, carbon dioxid and methane is determined before and 

 after passing the animal, the difference, of course, showing how 

 much of each gas the subject has added. In an apparatus suit- 

 able for small animals the entire amount of carbon dioxid and 

 water in the incoming and outgoing air current may be deter- 

 mined, but in the larger forms it is necessary to measure the air 

 current and make analyses upon relatively small samples, so that 

 the analytical errors are multiplied by a large factor, while a de- 

 termination of the oxygen balance has not as yet been found 

 practicable. The general scheme of such an apparatus is shown 

 in the diagram, Fig. 27. As in the case of the Regnault-Reiset 

 apparatus, the respiration chamber may be replaced by a mask, 

 mouthpiece or cannula for the investigation of the pulmqnary 

 exchange. 



1 Ann. de Chem. et de Physique, 3^ me Series, 26, 299. 



2 Carnegie Institution of Washington, Publication No. 42 (1905). 

 8 Landw. Jahrb., 44 (1913), 776. 



4 Deut. Arch. Klin. Med., 107 (1912), 156. 



