1835.] 



on Respiration. 



29 



CARBONIC ACID. 



6 - 2-05 per cent. 



7 - 2-39 



8 - 3-85 



9 - 3-05 

 10 - 7.16 



I was not a little surprised at these results : the diffe- 

 rences being so much greater than I had anticipated. The 

 mean of the whole is 4*24 per cent., which, therefore, I am 

 disposed to consider as representing the mean quantity of 

 carbonic acid gas, contained in 100 volumes of air expired 

 from my lungs. 



I was naturally induced to examine the air from the lungs 

 of several other persons, in order to see whether there 

 would be the same difference in theirs as I had observed 

 with respect to myself. The gentlemen whose breathing 

 was examined, were chiefly those who were occupied with 

 practical chemistry in my laboratory. The following table 

 exhibits the results obtained : — , 



CARBONIC ACID. 



Mr. Thomas Thomson, (aged 14) 3*06 per cent. 



I prevailed upon two ladies to allow me to examine the 

 air from their lungs. The first was an unmarried lady 

 about seventeen years of age ; the second a married lady, 

 aged about thirty. The results were as follows : — 

 First lady - 2-35 | Second lady - 4*06 

 The diversity here is fully as great as in my own case, 

 but the mean of the whole does not differ much from that 

 of my own. I am disposed, therefore, to infer from these 

 trials, that the average volume of carbonic acid gas, in 100 



