4:02 RESPIRATION. 



is made which requires a temporary arrest of respiration. 

 Brief and violent muscular exertion is generally preceded by 

 a profound inspiration. In sleep, as the volume of breathing 

 air is somewhat increased, the complemental air is encroached 

 upon. .A part or the whole of the complemental air is also 

 used in certain vocal efforts, in blowing, in yawning, in the 

 deep inspiration which precedes sneezing, in straining, etc. 



Summary. In a healthy male of medium stature, the 

 residual air, which cannot be expelled from the lungs, 

 amounts to about 100 cubic inches. 



The reserve air, which can be expelled, but which is not 

 changed in ordinary respiration, amounts to about 100 cubic 

 inches. 



The tidal air, which is changed in ordinary respiration, 

 amounts to about 20 cubic inches. 



The complemental air, which may be taken into the 

 lungs after the completion of an ordinary act of inspiration, 

 amounts to about 110 cubic inches. 1 



1 In Robin's Journal de P Anatomic et de la Physiologie, Sept. 1864, p. 523 

 et seq., we find an article by Dr. Nestor Grehant, on the physical phenomena 

 of respiration in man, which contains some novel and interesting observations on 

 the capacity of the lungs, volume of breathing air, etc. The volumes of air are 

 estimated by a process which is exceedingly ingenious, and apparently accurate ; 

 but the number of observations is very small compared with those of Hutchinson, 

 and in estimating the capacity of the lungs, he does not take into consideration 

 the very decided influence of stature. The method employed is essentially the 

 following : 



It having been demonstrated by Regnault and Reiset that hydrogen intro- 

 duced into the lungs is not absorbed by the blood, the author, taking advantage 

 of the well-known property of gases, by which they form a uniform mixture when 

 brought in contact with each other, caused the subjects of his experiments to re- 

 spire a measured volume of hydrogen often enough to make the mixture uniform, 

 and estimates, by analysis of the expired "air, the quantity which remains in the 

 lungs, which is necessarily represented by the volume of hydrogen lost. He as- 

 certained by experiments that five respirations of the gas caused a perfect 

 mixture. 



By this method he estimates the normal capacity of the lungs after an ordi- 

 nary expiration (the sum of the residual and reserve air), at from 133*65 to 191'51 

 cubic inches, in men between 17 and 30 years of age (p. 554). 



