26 On Respiration and Animal Heat. 
forced expiration, I find it to contain 6 per 
cent. of acid, and to have lost nearly 8 per 
cent of oxygen. 
By frequent trials, I find the quantity of 
ar taken in at each natural inspiration by 
me, is about a pint, wine measure, or nearly 
30 cubic inches. This quantity is consider- 
ably less than some authors state it, and more 
than others. It is probable, that different 
subjects exhibit a difference in this respect ; 
but it can scarcely be so great as is represent- 
ed. I find, too, that in a state of quiescence, 
I take 20 inspirations in a minute. This 
gives 500 cubic feet of atmosphericair inspired 
in a day, =46,5lbs. troy, of which 105 is 
oxygenous gas, and 25 of this enters into new 
combinations. This will be found to weigh 
45120 grains=2,6lbs. troy.—By a full forced 
inspiration, my lungs can contain about 7 
pints or 200 cubic inches of air, which can be 
expelled again by a forced expiration; the 
quantity still remaining in the lungs, after 
such expiration, is not easily to be determined ; 
it cannot however be much, and it is of little 
consequence to know it exactly. It appears 
then, that after an ordinary expiration, my 
lungs still contain 3 pints of air; and that 
after an ordinary inspiration there is still reom 
left for 3 pints more. 
