THE BALANCE OF NUTRITION 



2OQ 



tion and replace the oxygen consumed or to conduct a current 

 of air through the apparatus. Correspondingly, two different 

 types of respiration apparatus have been evolved, known re- 

 spectively as the closed circuit and open circuit apparatus, 

 or, from the names of the investigators who first developed them 

 into practicable appliances, as the Regnault-Reiset and the 

 Pettenkofer apparatus. Each of these two types may be sub- 

 divided into those intended to determine the total gaseous ex- 

 change of an animal and those which take account only of the 

 pulmonary exchange. 



298. The Regnault-Reiset apparatus. In the closed cir- 

 cuit, or Regnault-Reiset apparatus, respiration takes place in 



RESPIRATION CHAMBER 

 used 



FIG. 24.- 



Scheme of closed circuit respiration apparatus. (Atwater and Benedict, 

 Carnegie Institution of Washington, Publication No. 42.) 



a confined volume of air, the possibility of any exchange be- 

 tween it and the outside atmosphere being carefully guarded 

 against. By suitable mechanical means (a blower, for instance) 

 the confined air is kept in circulation over suitable absorbents 

 which take up the water and carbon dioxid given off, while 

 the oxygen consumed is replaced from a gasometer or a cylinder 

 of the compressed gas. The general scheme for such an ap- 

 paratus is shown in Fig. 24. The increase in weight of the' ab- 

 sorbents plus any increase in the amount of carbon dioxid and 



