METHODS OF MEASURING RESPIRATORY EXCHANGE 23 



Daodsp. '} 

 QiZcc. '--. 







I t</t7cmM 



airtight renders this type unsuitable for experiments on large animals, 1 

 in which also the difficulty and cost of dealing with the large quan- 

 tities of carbon dioxide 

 produced constitutes a 

 very serious drawback. 



In experiments of a 

 long duration the excre- 

 tions of the animal may 

 render the use of a Reg- 

 nault apparatus very diffi- 

 cult. 



The air-current ap- 

 paratus are in general 

 much less complicated 

 and much cheaper both 

 initially and with regard 

 to working expenses than 

 closed-space apparatus of 

 corresponding dimensions. 

 They are therefore, and 

 also because they need 

 not be airtight, absolutely 

 to be preferred for experi- 

 ments on large animals 

 (from the size of man and 

 upwards) and also for 

 experiments on smaller 

 animals which have to 

 last long. When it is 

 desired to determine only 

 the carbon dioxide pro- 

 duced the air-current ap- 



FIG. 3. Krogh's micro-respiration apparatus. 

 " Biochem. Zeitschr.," 62, 267. 



From 



paratus can be of an especially simple and cheap construction. 



i. A. (a) Closed Space Respiration Apparatus. 

 The simplest form of a closed-space respiration apparatus is the 

 micro-respiration apparatus shown in fig. 3 (Krogh, 1914). It consists 



1 In the Regnault apparatus at the Landwirtschaftliche Hochschule in Berlin of 80 

 cub. metres a volume of 500 lit. air will often leak in (or out) during an experiment of 

 twenty-four hours in spite of every precaution being taken to keep the inside pressure as 

 near as possible the same as the atmospheric, 



