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THE POPULAR SCIENCE MONTHLY. 



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- 



ttSj 



7 



^ 



*K 



Fig 24 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 breath- 

 ing-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. 



blooded 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 trav- 

 eling 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 coun- 

 tries, but its abode is limited to central Europe, Asia Minor, and a 



