280 Messrs. Allen and Fepys on the Changes produced in 
inches of carbonic acid gas from his lungs in eleven minutes, 
and supposing the production uniform for twenty-four hours, 
the total quantity in that period would be 39534 cubic inches, 
weighing 18683 grains ; the carbon, in which is 5363 grains, 
or rather more than 11 oz. troy, the oxygen consumed in the 
same time will be equal in volume to the carbonic acid gas, 
but it is evident, that the quantity of carbonic acid gas, emitted 
in a given time, must depend very much upon the circum- 
stances under which respiration is performed ; and here it may 
be proper to notice that all the experiments were made be- 
tween breakfast and dinner. 
4. When respiration is attended, with distressing circum- 
stances, as in the 14th and 15th experiments, there is reason 
to conclude that a portion of oxygen is absorbed ; and in the 
last of these experiments, we may remark, that as the oxygen 
decreases in quantity, perception gradually ceases, and we 
may suppose that life would be completely extinguished on 
the total abstraction of oxygen. 
5. A larger proportion of carbonic acid gas is formed by 
the human subject from oxygen, than from atmospheric air. 
6. An easy, natural inspiration, is from 16 to 1 7 cubic 
inches in the subject of these experiments, who makes about 
39 in a minute ; this, however, will vary in different indivi- 
duals, and perhaps we ought to estimate the quantity of car- 
bonic acid gas, given oft' in perfectly natural respiration, at 
somewhat less, and most likely at considerably less, than in the 
statement above, when we consider that in short inspirations 
the quantity of air. which has reached no farther than the 
fauces, trachea, &c. bears a much larger proportion to the 
whole mass respired, than when the inspirations are deep. 
