134 



quantity of this gas did appear during the first in- 

 spirations ; and not after the supposed combination 

 of oxygen with the red particles of the blood. 



109. Mr Davy has breathed the nitrous oxide, 

 in a state of purity, for four minutes and a half, 

 and some have respired k five minutes ; and he 

 states the proportion of oxide absorbed to be as 

 great in the last, as in the first inspirations, the con- 

 sumption, by the same individual, being nearly in 

 the ratio of the time of respiration *. He thinks a- 

 bout a pint, or 30 cubic inches, to be the ordinary 

 range of consumption in different individuals, which, 

 he says, is not far from two cubic inches, or about 

 one grain every second ; or in one minute 120 cu- 

 bic inches, or 60 grains f. This quantity amounts, 

 in five minutes, to 600 cubic inches, or 300 grains ; 

 and in one hour, to 720O cubic inches, or 360O 

 grains ; equal to more than 31 gallons measure, or se- 

 ven ounces and a half troy weight, if it were possible 

 so long to continue respiring, and the consumption 

 were nearly in the ratio of the time of respiration. 

 But taking the proportion only for five minutes, 

 and allowing all that Mr Davy would deduct as li- 

 berated again from the blood in the same space of 

 time, it would amount to a bulk and weight alto- 

 gether inconsistent with what we know to be the 

 state and condition of the sanguiferous system ; and 

 the inference, if followed out, might therefore, in 

 the form of a reductio ad absurdum, be employed a- 

 gainst Mr Davy's opinion. 



* Researches, p. 425. f Ibid. p. 427. 



