Respiration 



ADDITIONAL EXPERIMENTS 



Experiment 82. To show how the lungs may be filled with air. 

 Take one of the lungs saved from Experiment 78. Tie a glass tube 

 six inches long into the larynx. Attach a piece of rubber to one end 

 of the glass tube. Now inflate the lungs several A 



times and let them collapse. 



Experiment 83. To show that the expired air 

 contains carbon dioxide. Put a glass tube into a 

 bottle of lime water and blow through the tube. 

 The liquid will soon become cloudy, because the 

 carbon dioxide of the expired air unites with the 

 lime held in solution and forms the white, solid 

 carbonate of lime. 



Experiment 84. To illustrate the manner in 

 which the movements of inspiration cause the air 

 to enter the lungs. Fit up an apparatus, as repre- 

 sented in Fig. 93, in which a stout glass tube is 

 provided with a sound cork, B, and also an air- 

 tight piston, D, resembling that of an. ordinary 

 syringe. A short tube, A, passing through the 

 cork, has a small India-rubber bag, C, tied to it. 

 Fit the cork in the tube while the piston is near 

 the top. Now, by lowering the piston, we increase 

 the capacity of the cavity containing the bag. The 

 pressure outside the bag is thus lowered, and air 

 rushes into it through the tube, A, till a balance 

 is restored. The bag is thus stretched. As soon 

 as we push up the piston, the elasticity of the bag, 

 being free to act, drives out the air just taken in, 

 and the piston returns to its former place. 



In this experiment the elastic bag and its tube 

 represent the lungs and trachea, and the glass vessel enclosing it rep- 

 resents the thorax. It must be remembered, however, that the space 

 between the wall of the thorax and the outside of the lung is a vacuum. 



FIG. 93. 



Apparatus for 



illustrating the 



Movements of 



Respiration. 



