132 



Mr Davy, from the results of his experiments, has 

 been led to revive this opinion concerning the en- 

 trance of nitrogen into the blood. In the respiration 

 of atmospheric air, he calculates that 5.2 cubic inches 

 of nitrogen disappear every minute * : and when 

 nitrous oxide is breathed, he supposes that " an im- 

 mense quantity of this substance is taken into the 

 blood ; and that the part of it not expended in new 

 combinations, during living action, is liberated in the 

 aeriform state by the exhalents, or through the moist 

 coats of the veins f." But why the blood should so 

 much more powerfully attract nitrogen from nitrous 

 oxide than from atmospheric air, is enough of it- 

 self to beget doubts of the truth of Mr Davy's con- 

 clusion, more especially if we consider, that " nitro- 

 gen and oxygen exist, perhaps, in this oxide in the 

 most intimate union which those substances are ca- 

 pable of assuming J." The only direct evidence in 

 favour of this opinion, is the loss in bulk which ni- 

 trous oxide suffers in respiration. For this we have 

 endeavoured to assign an adequate cause (9 1 . et seq.); 

 and a reference to Mr Davy's experiments (92.) will 

 shew, that when he breathed this oxide once only, 

 the loss in bulk was one-twelfth ; when twice, the 

 loss was about one-eighth ; and when seven times, 

 the loss amounted to more than one-third ; thus re- 

 gularly increasing with the repeated respiration of a 

 noxious gas, and consequent debility of the expira- 

 tory powers, just as takes place in the repeated 

 breathing of the same volume of atmospheric air. 



* Researches, p. 434. f Ibid. p. 415. f Ibid, p. 328. 



