Section XXIX of essays on “Classification,” complete.

THOUGH it had long been known, by the experiments of De Saussure, that the breathing processes of animals and plants are very different, and that while the former inhale atmospheric air, and exhale carbonic acid gas, the latter appropriate carbon and exhale oxygen, it was not until Dumas and Bousingault called particularly the attention of naturalists to the subject, that it was fully understood how direct the dependence is of the animal and vegetable kingdoms one upon the other, in that respect, or rather how the one consumes what the other produces, and vice versâ, thus tending to keep the balance which either of them would singly disturb to a certain degree. The common agricultural practice of manuring exhibits from another side the dependence of one kingdom upon the other: the undigested particles of the food of animals return to the ground, to fertilize it for fresh production. Again, the whole animal kingdom is either directly or indirectly dependent upon the vegetable kingdom for its sustenance, as the herbivorous animals afford the needful food for the carnivorous tribes. We are too far from the time when it could be supposed that worms originated in the decay of fruits and other vegetable substances, to need here repetition of what is known respecting the reproduction of these animals. Nor can it be necessary to show how preposterous the assumption would be that physical agents produced plants first, in order that from these, animals might spring forth. Who could have taught the physical agents to make the whole animal world dependent upon the vegetable kingdom?

  On the contrary, such general facts as those above alluded to show, more directly than any amount of special disconnected facts could do, the establishment of a well-regulated order of things, considered in advance; for they exhibit well-balanced conditions of existence, prepared long beforehand, such as only an intelligent being could ordain.