44 On Respiration and Animal Heat. 
than that in the veins.” Query, does this mean that the 
blood in the arteries approached to that in ‘the veins in 
colour; or vice versa ; or neither of these, but that they 
mutually approached to each other in colour? Upon the 
whole the production of carbonic acid from oxygen and car- 
bone without the evolution of heat (sensible or otherwise), 
in the animal system or any where else, would be a 
phenomenon so extraordinary in chemistry, that very direct 
and precise evidence of the fact must be adduced, beforg | 
it could be generally admitted, 
