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Page:Popular Science Monthly Volume 21.djvu/623

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pocket-knife into its handle. The fangs of the scorpion are modified feet.

Certain fishes have the power of storing a large quantity of electricity, which is used at will to paralyze and kill prey or enemies. The electric eel can kill small fishes at a distance, it is said, of fifteen feet; and they sometimes kill the horses which are driven into the pools for the purpose of exhausting and capturing the eels. The electricity, is stored in a peculiar tissue of large cells or tubes which act like a battery of so many Leyden-jars. Apparently nervous force is here converted into electricity. After giving several shocks, the creature is exhausted for a time. PSM V21 D623 The torpedo ray with its electrical apparatus displayed.jpgFig. 11.—The Torpedo, with its Electrical Apparatis displayed. b, branchiæ; c, brain; e, electric organ; g, cranium; me, spinal cord; n, nerves to the pectoral fins; nl, nervi laterales; np, branches of pneumogastric nerves going to the electric organ; o, eye. Besides those creatures which are passively offensive by their odors, there are others which can at will expel fluids to offend and deter enemies. The skunk need only be named, and the point will be fairly grasped by the reader. Some reptiles have the power to expel an offensive fluid from glands in the skin. The toad and salamander are examples. This fluid is acrid and biting, and intensely irritating to delicate skin, as the mucous membrane of the mouth or eye. The abundance of this viscid yellow fluid in the salamander probably led to the ancient notion that this little amphibian could withstand and extinguish fire. The water-beetle (Dytiscus) also expels a nauseating fluid.

It is very curious to find how some weak and lowly creatures succeed in frightening away their powerful foes. They assume a virtue which they do not possess. The attitudes of some insects may also protect them, as the habit of turning up the tail, by the harmless rove-beetles, no doubt leads other animals, besides children, to the belief that they can sting. The curious attitude assumed by sphinx caterpillars is probably a safeguard, as well as the blood-red tentacles which can suddenly be thrown out from the neck by the caterpillars of all the true swallow-tailed butterflies."

Many creatures produce sounds for the same purpose. The cat spits. Snakes hiss. The porcupine rattles his quills. "Even the preliminary rustle of the quills with which a porcupine generally prepares every attack is sufficient to make an ordinary horse flee in terror." Perhaps the sounds produced by certain naked sea-snails are in some degree for defense.