"_Our screen's broken_," said the voice, suspiciously, "_but we have a sick cow. It was dumped on us night before last. Cure her and we'll accept it as identification._" Calhoun could hardly believe his ears. This was an emergency situation! The curing of a sick cow was considered more convincing than a Med Ship man's regular credentials! Such a scale of values hinted at more than a mere isolation syndrome. There were thousands of inhabited worlds, now, with splendid cities and technologies which most men accepted with the same bland confidence with which they looked for sunrise. The human race was civilized. Suspicion of a Med Ship was unheard of. But here was a world-- "Why ... certainly," said Calhoun blankly. "I suppose I may go outside to ... ah ... visit the patient?" "_We'll drive her up to your ship_," said the high, tense voice. "_And you stay close to it!_" Then it said darkly. "_Men from Two City sneaked past our sentries to dump it on us. They want to wipe out our herd! What kind of weapons have you got?_" "This is a Med Ship!" protested Calhoun. "I've nothing more than I might need in an emergency!" "_We'll want them anyhow_," said the voice. "_You said you need to find out where you are. We'll tell you, if you've got enough weapons to make it worth while._" Calhoun drew a deep breath. "We can argue that later," he said. "I'm just a trifle puzzled. But first things first. Drive your cow." He held his head in his hands. He remembered to throw off the spacephone and said: "Murgatroyd, say something sensible! I never ran into anybody quite as close to coming apart at the seams as that! Not lately! Say something rational!" Murgatroyd said, "_Chee?_" in an inquiring tone. "Thanks," said Calhoun. "Thanks a lot." He went back to the ports to watch. He saw men come out of the peculiar agglomeration of buildings that had been piled around the grid's sturdy control building. They were clothed in cloth that was heavy and very stiff, to judge by the way it shifted with its wearers' movements. Calhoun wasn't familiar with it. The men moved stolidly, on foot, across the incredible pasture which had been a landing space for ships of space at some time or other. They reached a spot where a dark animal form rested on the ground. Calhoun hadn't noticed it particularly. Cattle, he knew, folded their legs and lay down and chewed cuds. They existed nearly everywhere that human colonies had been built. On some worlds there were other domestic animals descended from those of Earth. Of course there were edible plants and some wholesome animals which had no connection at all with humanity's remote ancestral home, but from the beginning human beings had been adjusted to symbiosis with the organic life of Earth. Foodstuffs of non-terrestrial origin could supplement Earth-food, of course. In some cases Earth-foods were the supplements and local, non-terrestrial foodstuffs the staples. But human beings did not thrive on a wholly un-Earthly diet.