146 



was partly founded, no longer exist, yet it should 

 never be forgotten that his experiments and discove- 

 ries first pointed out the true path of investigation ; 

 and have contributed, in a pre-eminent degree, to 

 advance our knowledge of this most important 

 function. The cause of the unfitness of air, beyond 

 a certain extent, to support life and flame, he proved 

 to arise from the destruction of its pure part, or 

 what has since been called its oxygen gas ; and he 

 concluded, that, by the several processes of respira- 

 tion, combustion, and calcination, it underwent pre- 

 cisely the same changes *. M. Lavoisier, in the 

 following year, investigated these changes with great- 

 er accuracy. He confirmed the fact of the disap- 

 pearance of oxygen gas during respiration ; and add- 

 ed, that the residual air of this process differed 

 from that left after the calcination of metals in con- 

 taining a quantity of carbonic acid t ; thus verifying 

 also the fact discovered more than twenty years be- 

 fore by Dr Black. 



118. Whence then is this carbonic acid, which is 

 formed in respiration, derived ? In the several process- 

 es of germination, of vegetation, and of respiration in 

 the inferior classes of animals, it has been shewn, that y 

 as carbonic acid is formed, the oxygenous portion of 

 the air gradually and completely disappears ; and that 

 the acid produced bears always a constant proportion 

 to the oxygen gas lost. We have now to shew, that 



* Philosophical Transactions, 1776. 

 f Mem. Acad. 1777, 



