[ * 2 3 ] 



ftate with more propriety than 

 that glafs exifts actually in our 

 body, becaufe, by the action of 

 lire, our body may be changed in 

 a conftituent part of that fubftance ; 

 and that fat exifts in grafs and other 

 vegetables, becaufe in the organs of 

 an animal feeding upon thefe herbs 

 they are partly changed into fat. 

 Thus, when we feed upon vegeta- 

 bles, we do not in reality take in 

 fixed air, exifting as fuch in the fub- 

 ftance of that food, and only let loofe 

 or extricated in our bowels ; but it is 

 more probable, that fuch food, un- 

 dergoing in our ftomach and intef- 

 tines a kind of fermentation, yields 

 really fixed air, not extricated, but 

 generated by the act of fermentation. 

 As we have feen now, that com- 

 mon air is far from being an un- 

 alterable fluid, only to be changed 



by 



