LABORATORY MANUAL OF PHYSIOLOGY. 



der in the tub", record and repeat the operation until all the spirom- 

 eter scale is estimated in terms of cubic centimetres of the testing 

 graduated cylinder. 



(b) Tidal Air. With the pointer of the spirometer at the zero 

 mark of the scale, expire into the spirometer cylinder after an or- 

 dinary inspiration. The amount of expired air recorded is an ap- 

 proximate indication of the tidal air, i.e., the amount that passes 

 in and out of the lungs during quiet respiration. 



(c) Supplemental Air. Repeat the spirometer record, taking a 

 normal quiet inspiration, and then forcing as much air out of the 

 lungs as possible. Read the record on the spirometer scale. Sub- 

 tract the reading of (b) from' the latter reading. The difference is 

 the so-called supplemental or reserve air. This is the amount of 

 air which remains in the lung after a quiet expiration and which 

 may be expelled by a forced expiration. After this is expelled, air 

 still remains in the lung which cannot be forced out. This is the 

 residual air. The air which can be inspired in addition to the or- 

 dinary inspiration is known as the complemental air. 



(d) Vital Capacity. Take the deepest possible inspiration, and 

 empty the lungs as completely as possible into the spirometer 

 cylinder by a forced expiration. The record obtained indicates 

 the full pulmonary capacity minus the residual air, and is equal 

 to the sum of the tidal air, complemental air, and supplemental air. 

 This is known as the vital capacity. 



Record the vital capacity of each member of your group, and 

 compare with the various chest measurements already taken. 



7. Cardio-pneumatic Movements. The changes in volume of 

 the heart during systole and diastole cause corresponding changes 

 in the capacity of the thorax and consequently of the lungs. The 

 inspiratory and expiratory movements caused by the heart-beat 

 may be demonstrated in the following manner: Bend one end of 

 a medium large piece of glass tubing into the form of a U. Fill the 

 bend of the U with a little water colored with eosin. Place the end 

 of the horizontal limb of this tube in one nostril. Close the other 

 nostril with the finger and keep the mouth closed. Hold the 



