CHAPTEE XXI 



METHODS OF STUDY OF GAS EXCHANGE. MAIN- 

 TENANCE METABOLISM AND GROWTH. ENERGY 

 EXCHANGE AFTER INGESTION OF FOOD 



IN the course of these lectures reference has frequently 

 been made to estimation of the volume of gas exchange, of 

 the respiratory quotient and similar matters. An explana- 

 tion of the methods which we have at our disposal for de- 

 termining these values has, however, not been presented, and 

 the opportunity should be taken at this time to repair this 

 neglect, by at once outlining the technic of the modern study 

 of gaseous metabolism 1 as fully as seems to pertain to gen- 

 eral biochemical training. 



METHODS OF GAS EXCHANGE STUDIES 



Pettenkofer Type of Respiration Apparatus. A respira- 

 tion experiment may be conducted on Pettenkofer 's principle 

 by placing the individual concerned in an enclosed space 

 through which a current of air is passed by a pump mechan- 

 ism. The volume of the air is measured by means of a gas- 

 meter, and an aliquot portion is analyzed for its water and 

 carbonic acid by means of sulphuric acid- and baryta-re- 

 ceivers. The respiration apparatus of Sonden and Tiger- 

 stedt, the respiration chamber of which, a room lined with 

 sheet zinc, is large enough to accommodate a number of per- 

 sons at the same time, works on this principle; but the gas 

 samples from it are analyzed by a volumetric method. The 

 method is very exact, the error in carbonic acid (as shown by 

 control experiments in which known amounts of oil were 



1 Literature upon Respiration Apparatus : A. Jaquet, Ergebn. d. Physiol., 

 2, 458-462, 1902; W. 0. Atwater, ibid., 3, 498-512, 1904; A. Magnus-Levy, 

 Handb. d. Pathol. d. Stoffw., 2d ed., 1, 198-212, 1906; A. Loewy, Handb. d. 

 Biochem., 4', 133-144, 1908; O. Cohnheim, Physiol. d. Verdauung und Ernah- 

 rung, pp. 360-365, 1908. 



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