DETERMINATION OF CARBON DIOXIDE AND OXYGEN 



329 



of the mercury manometer or by a graduated Marey's tambour. Connect 

 a piece of gas tubing with the proximal limb of the mercury manometer and 

 provide it with a glass mouthpiece. Insert this mouthpiece well back into 

 the cavity of the mouth, closing the lips firmly about it, keeping the 

 pharynx relaxed. Note the variations in pressure at the height of ordinary 

 inspiration and expiration through the nasal passages. Repeat with 

 forced inspiration and expiration, close the nasal passages, and make the 



FIG. 246. Chart showing transverse section of the chest at the level of the 

 mamma of a distance runner, age twenty-one, height, 5 feet, n inches, net weight, 140 

 T^nnrie ]? x i ? ordinary expiration; Ex*, forced expiration; In 1 , ordinary inspiration; 



pounds. 



In 2 , forced inspiration. 



Scale J. 



maximal expiratory and inspiratory effort. The manometer may be ad- 

 justed to write on the smoked paper or read directly. 



7. Demonstration of Carbon Dioxide in Expired Air. Arrange 

 two flasks, as in figure 246, filling each one-third full of baryta-water, or 

 lime-water. Close the lips around the mouthpiece of the apparatus and 

 inhale and exhale the air through it. The inspired air will come through 

 a, the expired air out through b. The baryta water in b will quickly 

 become clouded with a white precipitate of barium carbonate while that 

 in a will remain clear or only very slightly clouded, showing the excess of 

 carbon dioxide in expired air. 



8. Quantitative Determination of Carbon Dioxide and Oxygen in 

 Inspired Air and in Expired Air. Inspired Air. Fill a gas-analysis 

 apparatus, the Guthrie or any modern modification of the Haldane or the 

 Orsat analyzer, with air from outside the laboratory. Read the volume 



