"Even that should have tipped us off. There is a very fine line dividing incredible stupidity and incredible _stubbornness_. It's often a tough differential to make. I didn't spot it until I found them wolfing down the tetracycline capsules in my samples case. Then I began to see the implications. Those Mud-pups were stubbornly and tenaciously determined to drive the Piper Venusian Installation off Venus permanently, by fair means or foul. They didn't care how it got off--they just wanted it off." "But why? We weren't hurting them. There's plenty of mud on Venus." "Ah--but not so much of the blue-gray stuff we were after, perhaps. Suppose a space ship settled down in a wheatfield in Kansas along about harvest time and started loading wheat into the hold? I suppose the farmer wouldn't mind too much. After all, there's plenty of vegetation on Earth--" "They're _growing_ the stuff?" "For all they're worth," said Kielland. "Lord knows what sort of metabolism uses tetracycline for food--but they are growing mud that yields an incredibly rich concentration of antibiotic ... their native food. They grow it, harvest it, live on it. Even the way they shake whenever they come out of the mud is a giveaway--what better way to seed their crop far and wide? We were mining away their staff of life, my friend. You really couldn't blame them for objecting." "Well, if they think they can drive us off that way, they're going to have to get that brilliant intelligence of theirs into action," Simpson said ominously. "We'll bring enough equipment down there to mine them out of house and home." "Why?" said Kielland. "After all, they're mining it themselves a lot more efficiently than we could ever do it. And with Piper warehouses back on Earth full of old, useless antibiotics that they can't sell for peanuts? No, I don't think we'll mine anything when a simple trade arrangement will do just as well." He sank back in his cot, staring dreamily through the port as the huge orbital transport loomed large ahead of them. He found his throat spray and dosed himself liberally in preparation for his return to civilization. "Of course, the natives are going to be wondering what kind of idiots they're dealing with to sell them pure refined extract of Venusian beefsteak in return for raw chunks of unrefined native soil. But I think we can afford to just let them wonder for a while." Transcriber's Note: This etext was produced from "Tiger by the Tail and Other Science Fiction Stories by Alan E. Nourse" and was first published in _Fantastic Universe_ July 1957. Extensive research did not uncover any evidence that the U.S. copyright on this publication was renewed. Minor spelling and typographical errors have been corrected without note.