and of Contagious Difeafes. 1 79 



acid. If caloric, as a third principle, unite itfelf, fo as to fa- 

 turate the oxygen and azote at the moment of their extri- 

 cation, not to each refpectively, but as entering chemically 

 into union with each other, the remit will be a gas holding 

 the three ingredients chemically umted, and confequenily 

 pofTeffing very different properties from a mixture of oxygen 

 gas with azotic gas ; for, in the latter cafe, the bafe of each 

 having been previoufly faturated with caloric, both-the gales 

 by that means have been put into a ftate that prevents the 

 poflibility of a chemical union taking place between them. 



When a mere mixture of oxygen gas and azotic gas (at- 

 mofpheric air) is inhaled into the lungs, the animal powers 

 exert fuch an a£tion on the oxygen gas as to effect a fepara- 

 tion between the oxygen and caloric, applying each to the 

 purpofes intended by nature ; while the greater part of the 

 azotic gas is refpired undecompofed, mixed With the car- 

 bonic acid gas that has been generated by the union of a 

 portion of the oxygen gas with carbon furnilhed by the ani- 

 mal, and with moiffure formed by a portion of the bafe of 

 the oxygen gas with hydrogen, the caloric of that portion, 

 having gone to the fupply of the animal heat. But if a gas 

 compofed of oxygen and azote chemically combined with each 

 other and with caloric, be diffufed through the atmofpherc 

 inhaled, a fubftance is received into the lungs pofTeffing very 

 different chemical properties from common air; for, though 

 the component principles be the fame, being combined in a 

 very different manner, it muff poffefs a very different mode 

 of action upon the animal. In fact, it may be taken into 

 the fyftem in its combined ftate, where^ meeting with prin- 

 ciples which poffefs a ffronger affinity for fome of its confti- 

 tuent parts than they do for each other, it may be decom- 

 pounded ; while, by the fame operation, the animal fluids, or 

 folids, or both, arc themfelvcs decompounded, by parting 

 with one or more of their principles which enter into the 

 new combination, 



N » Where 



