kNtllbDUCTOIiY OBSERVATIONS, Xxxiii 



found perfeclly innoxious, nor any one equally 

 beneficial. The principal ingredients are faid to 

 be azotic gas, oxygen, carbonic acid, and water. 

 Azotic gas and carbonic acid are mofl pernicious 

 to animals, and the former conftitutes two-thirds 

 of the whole. By refpiration, a chemical pro- 

 cefs takes place, both in the fyflem of the refpir- 

 ing animal and in the air. A change is produc- 

 ed in the blood, and animal heat is promoted; 

 But the alteration that fucceeds in the fluid re- 

 fpired is of greater importance, for it is that 

 which occafions death in whatever manner it 

 may operate. The oxygen, or pure vital air, is 

 confumed ; an addition is made to the carbonic 

 acid gas, and almoft all the azot is left. Such 

 are the principal changes effefted by refpiration. 

 When this goes on in the open air, the continual 

 renewal of the f>ure parts, and the puriheation of 

 thofe unfit for ufe, the emanations and combina- 

 tions of Vv^hat arife from the fubilances in which 

 analogous operations are maintained, render it 

 again capable of being refpired without injury. 

 When the vital air is confumed, and the noxious 

 part remains behind, the pernicious effefts imme^ 

 diately become vifible. The manner in which 

 death enfues, like moft profound inveftigations, 

 has divided the opinion of philofophers. 



A^OL. L d Various 



