TYPES OF RESPIRATION APPARATUS 515 



burned) being scarcely greater than two per cent. Jaquet's 

 respiration apparatus is based upon the same principle. 



Regnault and Reiset Type of Respiration Apparatus. 

 The principle of renewal of a circulating current under- 

 lies the respiration apparatus of Eegnault and Eeiset, in 

 which the same body of air after having its carbonic acid 

 removed is constantly repassed through the respiration 

 chamber, the oxygen being renewed from a gas reservoir as 

 required. Although in its original form this apparatus was 

 only suited for the study of small animals, Hoppe-Seyler con- 

 structed a form on the same principle, the respiration cham- 

 ber of which afforded continuous accommodation for a hu- 

 man being, being of about five cubic metres dimension. A 

 more capacious and very much more satisfactory type on the 

 same principle may be seen in the large respiratory ap- 

 paratus constructed by N. Zuntz and C. Oppenheimer, in the 

 Physiological Institute of the Agricultural High School in 

 Berlin, with a capacity of eighty cubic metres. A tread mill, 

 enabling the performance of desired movements uphill and 

 downhill as well as exactly prescribed traction, is built in. 

 Moreover the trachea of an enclosed animal can be connected 

 by conducting tubes with measuring apparatus so that 

 separate study of pulmonary breathing and gas exchange 

 through the skin and intestine can be carried on. By means 

 of special provisions the apparatus makes it possible to have 

 any desired temperature, atmospheric moisture and (by fans ) 

 also any atmospheric movements act upon human beings, 

 to make changes in the proportions of oxygen and carbonic 

 acid in the air, and thus in some degree to produce artifi- 

 cially any sort of climate. The apparatus can be arranged 

 for employment on Pettenkofer's principle as well as on 

 that of Eegnault and Eeiset. Ordinarily it is used in the 

 latter manner, and the air for respiration purposes is chilled 

 in a tower seven metres high from contact with a system 

 of cooling pipes down to a temperature of 10 C., and ex- 



