Page:Popular Science Monthly Volume 17.djvu/496

480 which it swallows in masses as the whale does herrings; and while the whale spouts out through its nose the water it has swallowed and only retains the herring, the leech exudes the excess of water by means of a peculiar glandular apparatus in its skin, and keeps the infusoria in its maw. It also readily drinks the blood of cold-blooded and warm-blooded

 Arterial system, with the principal vessels (or heart) at the side, and their ramifications. 5 Venous system. 6. The intestinal canal, seen from the side: the round slime-sacs, or breathing-bladders, are situated between the folds of the maw. 7. The intestinal canal, seen from above: the upper part is the throat; the other parts represent the maw and intestines.

animals, and fills itself so greedily with the latter that it can not endure the surfeit, and dies soon afterward. Leeches were formerly abundant in the bogs and ponds of Germany, where, by reason of their great fruitfulness, they increased to millions, and were considered so worthless, even noxious, that the owners of the lands permitted the traveling dealers to fish them out at first for nothing, afterward for a small price. Finally the ponds were cleared of them; the dealers had sold the leeches for an immense profit, and millions on millions of them had been exported from Hamburg to America, and wherever else this costly and irreplaceable medical apparatus was needed, while the land of its production had none. The useful leech is not found in all countries, but its abode is limited to central Europe, Asia Minor, and a