260 



RESPIRATION 



at the end of an ordinary inspiration. Its amount varies, but may be reck- 

 oned as 100 cubic inches, or about 1,600 c.c. 



The Reserve Air is that which may be expelled by a forcible and deeper 

 expiration, after an ordinary expiration, such as that which expels the tidal 

 air. The reserve air amounts to from 1,200 to 1,500 c.c. This is also termed 

 the supplemental air. 



The Residual Air is the quantity which still remains in the lungs after 

 the most violent expiratory effort. Its amount depends in great measure 



FIG. 234. Tracing of the Normal Diaphragm Respirations of the Rabbit, a, With quick 

 movement of drum; b, with slow movement; /, inpiration; E, expiration. To be read from left 

 to right. (Marckwald.) 



on the absolute size of the chest, but may be estimated at about 1,000 c.c. 

 to 1,200 c.c. 



The total quantity of air which passes into and out of the lungs of an 

 adult, at rest, in 24 hours, is about 686,000 cubic inches. This quantity, 

 however, is largely increased by exertion; the average amount for a hard- 

 working laborer in the same time being 1,568,390 cubic inches. 



The Respiratory Capacity. The greatest respiratory capacity or vital 

 capacity of the chest is indicated by the quantity of air which a person can 

 expel from his lungs by a forcible expiration after the deepest possible in- 

 spiration. The vital capacity is the sum of the reserve, tidal, and comple- 

 mental airs. It expresses the power which a person has of breathing in the 

 emergencies of active exercise, violence, and disease. The average capacity 

 of an adult, at 15.4 C. (60 F.), is about 225 to 250 cubic inches, or 3,500 

 to 4,000 c.c. 



