"Here," said Calhoun, "are what look like plague microbes in their normal Delhian environment. They're sluggish and practically comatose. Phagocytes could take care of an invasion of them into a human body. But here—' He touched a culture bottle in which he had thriving plague microbes growing, cultured from a scrap of a dead man's clothing. "Here I have what may be the same bug in a Lanke environment. The bug is wildly active. It could cause the devil of a plague, on Lanke. I'm going to see what it would do on Delhi."
He looked up for an expression of interest. The girl looked unhappily at Rob. Calhoun stared, and frowned, and shrugged. He took up a pipette which might have been made for the smallest of dolls to use. He introduced dancing, swarming, preposterously proliferating microbes from the Lanke culture into the slide of Delhi swamp water.
Rob said harshly, "They're bringing a log to be a battering ram, since the sledge-hammer didn't work."
Calhoun looked at the outside vision screen. The log was moving slowly across the marshy ground on fifty pairs of feet. It looked like a monstrous creeping insect.
"They're stumbling," said Calhoun. "They can't batter while they're stumbling."
He turned back to the culture microscope. The half-drop of liquid from the pipette had contained thousands and thousands of the dark round microscopic spheres. They showed on the screen now: dancing, swarming, dividing into half-globes and growing back to full spheres again. Their activity was more than feverish. It was frantic.
In minutes it diminished. The dancings and dartings slowed. The infinitesimal objects ceased their headlong multiplication. They became languid. Gradually, they seemed to sleep. Now and again they made trivial, stagnant motions. They were not dead. They were not spores, they were no longer active. Calhoun regarded them with satisfaction. He said, "Ah-h-h!"
It was a most gratifying development. It couldn't have been observed on Lanke, because there was no Delhian material to show it. It couldn't have been seen on Delhi. There were no super-active specimens on Delhi. Only a Med Ship man could have made the observation, with Med Ship equipment. Calhoun looked triumphantly about. Elna still looked unhappily at Rob, and Rob still wore an air compounded equally of fury and of martyrdom.
"Murgatroyd," said Calhoun, "at least you'll be interested! Things are looking up!"
"Chee?" said Murgatroyd.
He padded across the floor and swung up to the lab table unfolded from the wall. Murgatroyd peered at the microscope screen as if it meant something to him. He said, "Chee-chee! Chee-chee!"
"Exactly!" said Calhoun. "This bug is comatose on Delhi, where there is no plague. It's wildly active on Lanke, where there has been, can be, and probably already is plague. We'll return these bugs to a Lanke environment."
He made it, distilled water and a nutrient substance for them to feed on. It was practically the environment of Lanke. He returned the just-made-comatose microbes to the sort of environment in which plague germs throve. These microbes regained all the enthusiasm of multiplication and dancing and—doubtless—the production of deadly toxins they'd shown before.
"Something on Delhi," said Calhoun, "slows down their activity and reduces their breeding rate as something on other worlds keeps the bigger predators from getting too numerous. Something here keeps their numbers down, and that something doesn't, on Lanke. What would you guess, Murgatroyd?"
Murgatroyd said, "Chee!" He moved about the lab table, with a very fine air of someone checking the various bits of equipment there. He picked up a culture slide. He sniffed at it and said, "Chee-chee!" in a very disapproving manner. He dropped it, and swamp water spilled. The odor was actively unpleasant. Murgatroyd sneezed, and retreated from it. He said, "Chee!" and rubbed his nose vigorously.
Calhoun shrugged. He mopped up the spilled half-spoonful. He had visions of living on a world where soil and swamp water stank when disturbed, and where even sea water might do the same. Where one boiled water before drinking it, not to make it germ-free but to drive out most of the taste. Elna had tasted normal water and had told Rob bitterly that she'd never taste water again without remembering how that pure water tasted.
He looked at the vision screens. There were fluffy white clouds in the bluest of blue skies. All oxygen atmosphere planets have blue skies, and those with habitability-one temperatures have winds and jet-streams and storm patterns of strictly standard types. On all the worlds with vegetation there were the equivalents of trees and brushwood and grass. The look of Delhi was not repellent, if one could only get used to the smell of the atmosphere, and not of the soil—if the reek of the swamp was simply an exaggeration of what everything smelled like and one could never fail to notice it . . . the passionate desire of its people to leave it could be understood.
The first log was almost at the Med Ship. A second was on the way. Smaller groups were bringing shorter logs. There were men coming with coils of rope.
Calhoun regarded them detachedly. He saw a man stumble and fall, and get up and be sick because of the stench of the mud he'd disturbed.
Calhoun went back to his work. He set out minute samples of swamp water, and added infinitesimal dosages of reagents to each, and then still more minute quantities of the Lanke environment, frantically active culture. Then a check to see what substance—or what substances made up a group—removed by a reagent would allow the spheres to thrive in swamp water.
It could almost have been predicted that the elaborate setup for research would be useless, and something insanely simple would give the answer. A strip of filter paper, wetted with the active culture and in a stoppered bottle with a trace of swamp fluid, that showed the active culture stopped dead. It did not touch swamp water. It was exposed only to the reekuotee stench, the effluvium of the swamp. Calhoun said, "The devil!" Painstakingly, he repeated the test. He wanted to talk about it, to explain it for his own hearing so that he'd know if his reasoning made sense. He said, "Murgatroyd!"
Murgatroyd said with an air of charmed interest, "Chee?"
"I've got it," said Calhoun. "There is something in the swamp water that slows up the plague germs in multiplying and producing toxin to kill us humans. It's an inhibitive factor like the factors that on different worlds make large carnivores breed slowly, because if they bred fast they'd wipe out their own food supply and die of starvation. In the micro-ecology of germs in Delhi, there's something that holds down plague germs so nobody can get the plague. But on Lanke that inhibitive factor's missing."
Murgatroyd said, "Chee!" and, beady-eyed, watched Calhoun's face.
"I'll bet you a hogshead of coffee to a cookie," said Calhoun exuberantly, "that it's nothing but the smell, the reek, the stink of that—Ha!" He referred to the Stellar Directory. He found Delhi. "Here it is! There's a methane derivative to point oh four percent in the planet's air, about the same as carbon dioxide. Maybe there's a bug in the ocean that produces it. Maybe—oh, anything! There are microbes that can't live where there's oxygen and others that can't live where it isn't. This is a microbe that can just barely live where there's point oh four percent of this stinking stuff. But it goes wild where there's . . . now! You see, Murgatroyd? A ship from here, with Delhi air, could go to Lanke and nobody'd have the plague. But a man from it would develop the plague when he got out into Lanke air which hasn't the methane that holds the plague-germ back. A ship from Lanke that left Delhi without Delhi air in its reserve tanks . . . everybody aboard would die of the plague on the way home. You see?"