288 
combustion, and its result an oxidation of the blood. 
To establish his theory of oxidation, M. Lavoisier 
trusted not to colour alone, but actually proved the 
combination and disengagement of oxygen, as the 
metal was alternately reduced or revived. In the pro- 
cess of oxidation, he remarked that the air lost one- 
sixth of its bulk, and contained no carbonic acid ; in 
that of respiration, the loss of bulk was only -fa* and 
a quantity of carbonic acid was produced. He even 
found that caustic alkali abstracted one-sixth of its 
bulk from air that had been respired, and therefore 
concluded that such air contained one-sixth of carbo- 
nic acid ; and after this acid gas was abstracted, the 
residue exactly resembled that left by the calcination 
of metals *. 
580. Thus, then, it appears, that although, in these 
experiments, M. Lavoisier distinctly ascertained, that, 
in oxidation, all the oxygen combined with the me- 
tal, and no carbonic acid was formed; and, on the con- 
trary, that, in respiration, all the oxygen was convert- 
ed into carbonic acid, and none therefore could com- 
bine with the blood ; yet he, nevertheless, supposed 
this oxygen to unite with the blood, and to pro- 
duce effects in it similar to those which followed the 
actual combination of this element with metallic mat- 
ter. M. Lavoisier and his associates exclaimed loud- 
ly against their predecessors for employing phlogiston 
as a principle, which, like another Proteus, was able 
to exhibit every colour, and to assume every shape *; 
but we may safely assert, that there is scarcely any 
* Mem. tie I'Acad. 1777, p. 185. t .Ib.-an. 1789, p. 508. 
