the logic of Aristotle, was utilized in the service of the Church, and the union of the Church and philosophy was irresistible, and enthralled the human mind for three centuries.
Thus the logic of Aristotle, which was never intended as anything but a defense against philosophical error, was turned into a system for the discovery of truth and scientific investigation. Aristotle himself would have been the first to protest against this misuse of it. The labors of the men were prodigious, but they were utterly barren of results—as barren as the labor on the tread-mill.
| HOW ANIMALS BREATHE. |
By HERMAN L. FAIRCHILD.
II.
SPECIAL ORGANS OF THE FOOD-TRACT.—Another class of respiratory organs may now be distinguished, namely, those developed directly from the alimentary canal. Here belong the more highly specialized organs of the vertebrates.
Aquatic Organs of the Food-Tract.—The gills or branchiæ of fishes are analogous in position and structure to those of crabs, but are morphologically different, as they are not developed from the skin directly, but from the lining of the pharynx. A powerful heart impels the blood rapidly through the gills, while these are bathed by water-currents produced by the pumping action of the mouth; so that rapid and constant changes are effected in both the blood and the aërating water. The branchiæ are comb-like fringes of minute blood-vessels,
placed on bony arches, having a complex structure, and beautifully adapted to their purpose of exposing a great amount of blood in small space and in brief time.
It is impracticable to describe at length the various arrangements
