METHODS FOR DETERMINING RESPIRATORY EXCHANGE. 869 



REGNAULT and REISET'S Method. According to this method the animal 

 or person experimented upon is allowed to respire in an inclosed space. The 

 carbon dioxide is removed from the air, as it forms, by strong caustic alkali, from 

 which the quantity may be determined, while the oxygen is replaced continually 

 in exactly measured quantities. This method, which also makes possible a direct 

 determination of the oxygen used as well as the carbon dioxide produced, has 

 since been modified by other investigators, such as PFLUGER and his pupils, SEEGEN 

 and NOWAK, and HOPPE-SEYLER, ROSENTHAL and OPPENHEIMER and especially 

 by ATWATER and BENEDICT. 1 



PETTENKOFER'S Method. According to this method the individual to be 

 experimented upon breathes in a room through which a current of atmospheric 

 air is passed. The quantity of air passed through is carefully measured. As it 

 is impossible to analyze all the air made to pass through the chamber, a small 

 fraction of this air is diverted into a branch line during the entire experiment, 

 carefully measured, and the quantity of carbon dioxide and water determined. 

 From the composition of this air the quantity of water and carbon dioxide con- 

 tained in the large quantity of air made to pass through the chamber can be 

 calculated. The consumption of oxygen cannot be directly determined in this 

 method, but may be calculated indirectly by difference, which is a defect in this 

 method. The large respiration apparatus of SONDEN and TIGERSTEDT as well 

 as of ATWATER and ROSA 2 are based upon this principle. 



SPECK'S Method. 3 For briefer experiments on man SPECK used the follow- 

 ing: He breathes through a mouthpiece with two valves, closing the nose with a 

 clamp, into two spirometer-receivers, where the gas-volume can be read off very 

 accurately. The air from one of the spirometers is inhaled through one valve 

 and the expired air passes through the other into the other spirometer. By means 

 of a rubber tube connected with the expiration-tube an accurately measured part 

 of the expired air may be passed into an absorption-tube and analyzed. 



ZUNTZ and GEPPERT'S Method.* This method, which has been improved by 

 ZUNTZ and his pupils from time to time, consists in the following: The individual 

 being experimented upon inspires pure atmospheric air through a very wide feed- 

 pipe leading from the open air, the inspired and the expired air being separated by 

 two valves (human subjects breathe with closed nose by means of a soft-rubber 

 mouthpiece, animals through an air-tight tracheal canula). The volume of the 

 expired air is measured by a gas-meter and an aliquot part of this air collected and 

 the quantity of carbon dioxide and oxygen determined. As the composition of 

 the atmospheric air can be considered as constant within a certain limit, the 

 production of carbon dioxide as well as the consumption of oxygen may be readily 

 calculated (see the works of ZUNTZ and his pupils). 



HANRIOT and RICHET'S Method 5 is characterized by its simplicity. These 

 investigators allow the total air to pass through three gasometers, one after the 

 other. The first measures the inspired air, whose composition is known. The 

 second gasometer measures the expired air, and the third the quantity of the 



1 See Zuntz in Hermann 's Handbuch, 4, Thl. 2, and Hoppe-Seyler, Zeitschr. f . 

 physiol. Chem., 19; Rosenthal, Arch. f. (Anat. u.) Physiol., 1902; Zuntz and Oppen- 

 heimer, Arch. f. (Anat. u.) Physiol., 1905, and Bioch. Zeitschr., 14; Atwater and 

 Benedict, Bull. Dept. of Agriculture, Washington, 69, 109, and 136. See also Krogh, 

 Wien. Sitz. Ber., 115, III., and Skand. Arch. f. Physiol., 18. 



2 Pettenkofer's method; see Zuntz, 1. c.; Sond4n and Tigerstedt, Skand. Arch, 

 f. Physiol., 6; Atwater and Rosa, Bull, of Dept. of Agriculture, 63. Washington. 



8 Speck, Physiologic des menschlichen Atmens. Leipzig, 1892. 



4 Pfliiger's Arch., 42. See also Magnus-Levy in Pfliiger's Arch., 55, 10, in which 

 the work of Zuntz and his pupils is cited. 



5 Compt. Rend., 104. 



