LABORATORY MANUAL OF PHYSIOLOGY. 



sorbing the carbon dioxid of the expired air. This tube also has 

 a bulb containing CaCl 2 . 



Tube 4 is connected with the water pump P. Air is drawn 

 through the system of tubes and respiratory chamber in the di- 

 rection of the arrow. 



1. Set up the apparatus as described, and allow the air to be 

 drawn through for fifteen or twenty minutes or until the respira- 

 tory chamber has been freed from moisture and carbon dioxid. 

 Now place the mouse in the chamber, stopper quickly, and weigh. 

 Also quickly weigh tubes 3 and 4. Make a record of the weights 

 for use later. Connect up the absorption tubes with the chamber 

 and air pump, and allow a current of air to pass through the system 

 for twenty minutes to one-half hour. Then disconnect and weigh 

 the chamber and absorption tubes again. 



The difference between the two weighings of the respiratory 

 chamber indicate the loss, in part, of the animal, in water and CO 2 . 

 The difference between the weighings of the absorption tubes in- 

 dicates their gain in water and CO 2 , respectively, and the actual 

 output of the animal in carbon dioxide and water, during the 

 time of the experiment. The difference between the two weigh- 

 ings of the respiratory chamber and the difference between 

 the two weighings of the absorption tubes do not correspond, 

 since what the animal has lost in CO 2 it has partly regained in 

 oxygen. 



The gain in oxygen may be roughly determined by subtracting 

 the difference between weighings of chamber C from the difference 

 between weighings of tube 4. The ratio between the oxygen ab- 

 sorbed and the carbon dioxid expired is known as the respiratory 

 quotient. 



What is the respiratory quotient for the mouse experimented 

 upon? 



2. Remove the mouse from the respiratory chamber. Ventilate 

 the chamber again. Prepare and weigh a new set of absorption 

 tubes. Give the mouse some form of exercise, such as moving the 

 treadwheel of a squirrel cage. Place in the chamber and quickly 



[164] 



