S66 0/2 the Changes produced in Atmospheric Air, <5#c. 



when the contacts are repeated almost as frequently as possi- 

 ble, only 10 per cent, is emitted. 



The 12th and 13th experiments prove, that when the in- 

 spirations and expirations are rrtore rapid than usual, a larger 

 quantity of carbonic acid is emitted in a given time; but the 

 proportion is nearly the same, or about 8 per cent. The pro- 

 portions of carbonic acid gas, in the first and last portions of 

 a deep inspiration, differ as widely as from 3*5 to 9*5 per cent. 



3. Considering the 11th as a standard experiment, it ap- 

 pears that a middle-sized man, aged about thirty-eight years, 

 and whose pulse is seventy on an average, gives off 302 cubic 

 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 3^534 cubic 

 inches, weighing; 1SCS3 grains; the carbon in which is 

 5363 grains, o; 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 

 verv much upon the circumstances under which respiration 

 js performed ; and here it may be proper to notice, that alt 

 the experiments were made between 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 oxvgen is absorbed ; and in 

 the last of these experiments, we may remark, that as the 

 oxvgen decreases in quantitv, perception gradually ceases, 

 and we may suppose that life would be completely extin- 

 guished on the total abstraction of oxygen. 



I. 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 17 cubic 

 inches in the subject of these experiments, who makes about 

 lf> in a minute ; this, however, will vary in different indi- 

 Tiduals, and perhaps we ought to estimate the quantity of 

 carbonic acid <ias, given off in perfectly natural respiration, 

 at somewhat less, and most likely at considerably less, than 

 in the statement above, when we consider that in short inspi- 

 rations the quantity of air which has reached no further than 



the 



