There have been, of course, emergency measures against contagion all through human history. There was a king of France, on Earth, who had all the lepers in his kingdom killed. There have been ships and houses burned to drive out plague, and quarantines which simply interfered with human beings were countless. Calhoun's measure on Tallien was somewhat more dramatic than most, but it had good justification. He set fire to the planet's capital city. The little Med Ship swept over the darkened buildings. Her emergency rockets made thin pencils of flame two hundred feet long. She touched off roofs to the east, and Calhoun rose to see which way the wind blew. He descended and touched here and there.... Thick, seemingly suffocating masses of wood smoke flowed over the city. They were not actually strangling, but they created panic. There was fighting in Government Center, but it stopped when the mysterious stuff--not one man in a hundred had ever seen burning wood or smelled its smoke--the fighting stopped and all men fled when a choking, reeking blanket rolled over the city and lay there. It wasn't a great fire, considering everything. Less than ten per cent of the city burned, but ninety-odd per cent of the paras in it ceased to be paras. More, they had suddenly regained an invincible aversion to the smell of butyl mercaptan--even a modified butyl mercaptan--and it was promptly discovered that no normal who had smelled wood smoke became a para. So all the towns and even individual farmhouses would hereafter make sure that there was pungent wood smoke to be smelled from time to time by everybody. But Calhoun did not wait for such pleasant news. He could not look for gratitude. He'd burned part of the city. He'd forced paras to stop being paras and become ashamed. And those who hadn't become paras wanted desperately to forget the whole matter as soon as possible. They couldn't, but gratitude to Calhoun would remind them. He took appropriate action. With the grid operator landed again, and after the grid was operable once more and had sent the Med Ship a good five planetary diameters into space--some few hours after the ship was in overdrive again--Calhoun and Murgatroyd had coffee together. Murgatroyd zestfully licked his emptied tiny mug, to get the last least taste of the beverage. He said happily, "_Chee!_" He wanted more. "Coffee," said Calhoun severely, "has become a habit with you, Murgatroyd! If this abnormal appetite develops too far, you might start yawning at me, which would imply that your desire for it was uncontrollable. A yawn caused by what is called a yen has been known to make a man dislocate his jaw. You might do that. You wouldn't like it!" Murgatroyd did not reply.