166 



VOLUME AND CHANGES OF THE GAS. 



"The amount of air that can be expelled by the deepest expiration 

 Connection be- after the fullest inspiration" bears a singular relation to the 

 tiIn e and Pira ~ hei S lli of the individual, as was discovered by Dr. Hutch- 

 height, inson. " For every inch of stature from five to six feet, 

 eight additional cubic inches of air at 60 Fahr. may be thus given out." 

 The quantity of air which can be thus expelled for the stature of five feet 

 one inch is 174 cubic inches, and for six feet, 262. It is independent of 

 the absolute capacity of the chest. 



The diurnal amount of air introduced into the lungs has been variously 

 Volun- and estimated from 226 to 399 cubic feet. A part, from 4 to 6 

 changes of the per cent., of the oxygen thus introduced disappears in the 

 respired gas. J U ngs, anc i the expired air is charged with from 3 to 5 per 

 cent, of carbonic acid. But that nothing analogous to combustion occurs 

 in those organs is proved by their temperature, which is not higher than 

 that of other parts of the system. Moreover, carbonic acid can be with- 

 drawn from venous blood in a Torricellian vacuum, and still better by 

 agitating the blood with such gases as hydrogen and nitrogen, proving 

 that that gas pre-exists in the venous blood before its entiy into the 

 lungs, and is not formed in those organs, unless, indeed, it exists as a bi- 

 carbonate, as already mentioned. The quantity of carbonic acid thus 

 disengaged is less than the quantity of oxygen absorbed, because much 

 of the latter is consumed in the production of sulphuric and phosphoric 

 acids, which escape in the urinary secretion, as indeed does a large quan- 

 tity of carbonic acid itself. 



The experiments of Vierordt show that the expiration, in a state of 

 Vierordt's rest, contains 4.334 per cent, of carbonic acid; that, as the 

 experiments, number of respirations per minute increases, the percentage 

 amount of carbonic acid diminishes ; and that for every expiration, with- 

 out reference to its duration, there is a constant amount of carbonic acid, 

 namely, 2.5 per cent., to which we must add a second value, expressing 

 the quantity of carbonic acid, and which is exactly proportional to the 

 duration of the respiration, as is shown in the following table. 



Vierordt also estimates that, for the entire removal of the carbonic 

 acid from the blood, more than three hundred respiratory acts per minute 

 would be required. To some extent, the depth of the respiration will 

 compensate for want of frequency. Thus he shows that in an expiration 

 of double the usual volume, the quantity of carbonic acid removed is 



