140 



PRACTICAL PHYSIOLOGY 



tion of fat from carbohydrate and the reverse change, carbohydrate 

 from fat. 



The effect of muscular exercise upon the respiratory exchange is 

 most marked ; hard work may increase it five to ten times. 



For certain researches upon the respiratory exchange of man a 

 respiration chamber is required. Few laboratories possess such 

 an expensive apparatus, but the principles can be studied in the 

 simple form of respiration apparatus for mice. 



CHAPTER XXIII 

 RESPIRATION APPARATUS 



The Haldane-Pembrey Respiration Apparatus for the Mouse. 

 The apparatus is constructed as in Fig. 135. Each double absorp- 

 tion tube is fitted with a wire loop, so that the glass need not be 

 touched with the hand. The animal chamber a light beaker is 

 provided with a thermometer and is also fitted with a wire loop. 

 The moisture given off by the animal is absorbed by pumice satur- 

 ated with sulphuric acid in the tubes AB. The carbon dioxide is 

 removed by soda lime in the tube C, and the water given off by the 

 soda lime is caught by the sulphuric acid tube D. 



M N A B C D 



FIG. 135. The Haldane-Pembrey respiration apparatus for the mouse. 



The animal is weighed in the beaker (with the tubes closed) 

 before and after the experiment. A dummy beaker is placed in 

 the opposite scale pan. The tubes AB and CD are also weighed 

 against a dummy pair of tubes. During the weighings the exit 

 and entrance tubes are left unstoppered. By these means errors 

 due to condensation of moisture and changes of barometric pressure 

 or temperature are avoided, and the weighings can be carried out 

 to less than a milligramme. 



The air entering the chamber is freed from carbon dioxide and 

 water by soda lime in M and sulphuric acid pumice in N. The 

 amounts of water and carbon dioxide given off in fifteen minutes 

 are determined by the increase in weight of AB and CD respec- 

 tively. The amount of oxygen absorbed is found by subtracting 

 the loss in weight of the animal weighed in the chamber from the 

 total loss of carbon dioxide and water, for the animal absorbs 



