311 
brought into such state of contact, as to favour its 
union with the animal carbon. When, also, water 
is exposed to heat, its elastic fluids are in great part 
expelled, but the last portions of oxygen adhere 
with so much force, that they cannot be separated 
even by long continued ebullition ; yet M. M. Hum- 
boldt and Provencal found, that, in such water, fishes 
were able to respire, and to convert its remaining 
oxygen into carbonic gas, although the oxygen 
did not exceed T ^o of the volume of water employ- 
ed *. While this fact, therefore, points out the ad- 
mirable provision that is made, to secure to fishes, 
even under the most unfavourable circumstances, the 
due exercise of this necessary function, it indicates, 
at the same time, the existence of a strong attractive 
force between the animal substance and oxygen gas. 
So, likewise, in many experiments made by Spallan- 
zani, the volumes both of oxygen and nitrogen gases, 
placed in contact with animal substances, were, for a 
time, considerably diminished ; which must have been 
accomplished by some property in the animal sub- 
stance, independent of its living power. In the same 
manner, we have seen, that the cellular and fleshy leaves 
of certain plants are able to receive and contain a vo- 
lume of air superior to their own bulk (342.) ; but, 
perhaps, the chemical affinity, exerted bet ween this air, 
after its conversion into carbonic acid, and the saline 
ingredients of the plant, may be deemed sufficient to 
account for the phenomenon. In the experiments, 
however, of Mr Acton (217. ), dead vegetable matter 
* Mem. d'Arcueil, torn. ii. p, 3 SI. 2. 
