RESPIRATION. 



535 



complemental air, or the volume that can be inspired after the completion of an 

 ordinary inspiration (1 500 cubic centimeters) ; reserve or supplemental air, or 

 the volume that can be expelled after an ordinary expiration (1240-1800 cubic 

 centimeters) ; residual air, or the volume remaining in the lungs after the most 

 forcible expiration (1230-1640 cubic centimeters); and stationary air, or the 

 volume remaining in the lungs after ordinary expiration, and equal to 

 reserve air plus residual air (2470-3440 cubic centimeters). The volume of 

 residual air is different according to various observers, the estimates ranging 

 from 538 cubic centimeters by Kochs to 19,800 cubic centimeters by Neupauer. 

 The recent researches of Hermann and Jacobson * give 914.5 cubic centimeters 

 as the average of nine observations, the lowest measurement being 434 cubic 

 centimeters, and the highest 1023.2 cubic centimeters. 



Lung-capacity is the total quantity of air the lungs contain after the most 

 forcible inspiration, and is equal to the vital capacity plus the residual air. 



Bronchial capacity is the capacity of the 

 trachea and bronchi, and is equal to about 140 

 cubic centimeters. 



Alveolar capacity is the volume of air in 

 the smallest air-passages and alveoli, and is 

 greater during inspiration than during expira- 

 tion, and, of course, is altered in proportion to 

 the depth of these movements. After quiet 

 expiration it is equal to about 2000 to 3000 

 cubic centimeters; during quiet inspiration it 

 is increased about 500 cubic centimeters, and 

 during forced inspiration about 2000 cubic cen- 

 timeters; during forced expiration it is dimin- 

 ished about 1500 cubic centimeters. Between 

 the extremes of forced inspiration and forced 

 expiration the volume differs about 3J times. 



Vital capacity is the volume of air that can 

 be expired after the most forcible inspiration. 

 Averages obtained by Vierordt from the results 

 of the observations by various investigators are 

 3400 cubic centimeters for men and 2500 cubic 

 centimeters for women. Such investigations 

 are conducted by the aid of a spirometer (Fig. 

 138), which is a calibrated gasometer consisting 

 of a bell-jar submerged in water and counter- 

 poised. Communicating with the interior of 

 the jar is a tube through which the expired air 



is conducted. The subject makes the deepest possible inspiration and then 

 forcibly expires into the tube : the jar rises in proportion to the volume of 

 air admitted, and the extent of this rise may be read from the scale. 



1 Pfluger's Archiv fur Physiologic, 1888, vol. 43, pp. 230, 440. 



FIG. 138. Wintrich's modification of 

 Hutchinson's spirometer. 



