Humboldt’s Electric Eels
I have written about Humboldt’s “electric eel” experiment in the Amazon previously on this blog (Baron Von Humboldt and the Electric Eels ), but here is the account from the man himself.
“Under the name of tembladores (‘which make you tremble’) Spaniards confuse all electric fish. There are some in the Caribbean Sea, off the Cumaná coast.  […] Other tembladores, proper electric eels, live in the Colarado and Guarapiche rivers and several little streams crossing the Chaima Indian missions. There are many of them in the great South American rivers, the Orinoco, Amazon and Meta, but the strength of currents and the depths prevent the Indians from catching them. They see these fish less often than they feel their electric shocks when they swim in the rivers. But it is in the llanos, especially around Calabozo, between the small farm of Morichal and the missions de arriba and de abaxo, that the stagnant ponds and tributaries of the Orinoco are filled with electric eels. We wanted first to experiment in the house we lived in at Calabozo but the fear of the eel’s electric shock is so exaggerated that for three days, despite our promising the Indians two piastres for each one. […]
“Impatient of waiting, and having only obtained uncertain results from a living eel brought to us, we went to Can~o de Bera to experiment on the water’s edge. Early in the morning on the 19th March we  left for the little village Rastro de Abaxo: from there Indians led us to a stream, which in the dry season forms a muddy pond surrounded by trees, clusia, amyria and mimosa with fragrant flowers […] The Indians decided to fish with horses, embarbascar con caballos. It was hard to imagine this way of fishing; but soon we saw our guides returning from the savannah with a troop of wild horses and mules. There were about thirty of them, and they forced them into the water.
“The extraordinary noise made by the stamping of the horses made the fish jump out of the mud and attack. These livid, yellow eels, like great water snakes, swim on the water’s surface and squeeze under the bellies of horses and mules. A fight between such different animals is a picturesque scene. […] Several horses collapsed from the shocks received on their most vital organs, and drowned under the water. Others panting, their manes erect, their eyes anguished, stood up and tried to escape the storm  surprising them in the water. They were pushed back by the Indians, but a few managed to escape, stumbling at each step, falling onto the sand exhausted and numbed from the electric shocks.
“In less than two minutes two horses had drowned. The eel is about 5 feet long and presses all its length along the belly of the horse, giving it electric shocks. They attach the heart intestines and the plexus coeliacus of the abdominal nerves.” (58 – 60)
Alexander Von Humboldt. Jaguars and Electric Eels. Trans. Jason Wilson. London: Penguin, 2007.