OXYGEN RESPIRATION 5 1 



tube shown in the diagram has a ground glass joint and is the most satisfactory 

 type designed for the purpose. The system may be used only when all joints 

 are so closed that the color of the indicator remains constant at some point in its 

 working range for a period of an hour or more. 



For further details of the use and modification of this apparatus see various 

 papers in the Jour. General Physiology, 1918 to date, particularly those by 

 Parker (4:689. 1921-22; 7: 641. 1924-25; and others) who calibrated his 

 system and brought out the extreme delicacy of tliis method. Measurements of 

 rates may be made a few minutes apart and a continuous record kept for hours. 



A few workers have successfully modified the Katharometer (c/. Daynes, H. A. 

 Pfoc. Roy. Soc. London. .\. 97: 273-286. 1920) for use in plant and animal 

 respiration. The fluctuations in the readings of a galvanometer record the 

 changes in thermal conductivity of a gas mixture, which conductivity is lowered 

 by an increase in CO2 content. A good account of such a method and its results 

 is given by Waller, J. C. (New Phyt. 25: 109-118. 1926) while Noyons 

 (Arch. Neerland d. Physiol d. I'Homme et d. Anim. 7: 488-495. 1922) and 

 Weaver E. R. and others (Jour. Indus, and Eng. Chem. 12:359-366. 1920) 

 also explain the modifications necessary to the use of the method for detecting 

 minute changes in concentration of carbon dioxide. 



Two other important methods which can only be mentioned here are those 

 of O. Warburg (Biochem. Z. 152 : 51-63. 1924) and Barcroft (Jour, of Physiol. 

 37: 12. 1908). The general technique of using the latter in its various modi- 

 fications has already been mentioned briefly (p. 34). The details are well stated 

 by Straub in Abderhalden's Handbuch der biologischen Arbeitsmethoden. 

 Abt. IV, Teil 10, Heft i where other methods for biological gas analysis are also 

 described in detail. Both of these t>-pes of apparatus have been utilized in the 

 production of valuable work in respiration. Only small quantities of material 

 are needed but both methods are somewhat restricted as to the type of problem 

 for which they are best suited, that of Barcroft having been developed for studies 

 of blood, as was Van Slyke's volumetric method (Jour. Biol. Chem. 61: 523. 

 1924). — Ed. 



