VITAL CAPACITY. 249 



millimetre scale attached, fill it about half full with coloured 

 water, and to the proximal limb attach an india-rubber tube 

 with a T-piece and screw clamp, as in the other experiments. 

 Connect the tracheal cannula with the manometer tube, 

 tighten the screw clamp, and see that the water stands at 

 the same level in both limbs of the manometer. 



(b.) Open both pleurae without injuring the lungs. The 

 lungs collapse, and the water is depressed in the proximal 

 side of the manometer, and rises in the open limb. 



4. Elasticity of the Lungs. 



(a.) E/emove the whole of the front of the chest in the 

 rabbit already used. Observe the collapsed lungs. To the 

 tracheal cannula attach an india-rubber bag such as is used 

 with a spray-producer, and innate the lungs. Cease to pump 

 air into the lungs, and observe how they collapse. 



5. Hydrostatic Test. 



(a.) Cut out the lungs and the heart. Place them in 

 a vessel of water. The whole will float, as the lungs contain 

 so much air. Cut off a small piece of one lung, throw it 

 into water, it floats. This is the hydrostatic test. Compare 

 a piece of pneumonic lung, the latter sinks. 



6. Apnoea. Count the number of your own respirations per 

 minute. Take a series of rapid inspirations. Note that several 

 seconds elapse before the next inspiration. This is the period of 

 apncea. 



LESSON LVII. 



VITAL CAPACITY EXPIRED AIR- 

 LARYNGOSCOPE VOWELS. 



1. Vital Capacity. Estimate this on Hutchinson's spiro- 

 meter i.e., take the deepest possible inspiration, and then make 

 the deepest possible expiration, expiring into the mouthpiece of 

 the spirometer. 



