“Ugh,” Matsudo commented. “Please do not remind me of the infestation even now swarming in my bodily fluids. Next time you wish to inject me with alien parasites—”

“Symbionts,” Saul corrected quickly.

`—against which my body has no immune capability whatsoever—next time I will make the incision myself—from crotch to sternum!”

Saul could only grin as Matsudo ’s serious mug broke and the man actually giggled. It was a “kee-kee-kee” sound that spacers had already mimicked into a sort of clarion call below decks. Akio frequently made such light jests about the traditions of ancient Japan.

Perhaps it was similar to the way Saul dropped Yiddishisms into his speech now and then, although he had learned the language only a decade ago. It’s a proper dialect for exiles, he thought.

“What have you got there, ’Kio?” He pointed at a flimsy sheet in the other’s hand.

“Ah. Yess.” Matsudo tended to slur his sibilants. “Even as we are speaking of immune systems, I have come to ask you to go through the stimulants inventory with me, Saul. I believe that it is time to release an attenuated disease into the life-support system.”

Saul winced. He never looked forward to this.

“So soon? Are you sure? Four-fifths of the expedition is still frozen aboard the Sekanina and the other freighter tugs. All we have awake now are the Edmund crew and support staff.”

“All the more reason.” Matsudo nodded. “Thirty spacers have been living together on this cramped ship for more than a year. Another forty have been out of the slots for two or more months, as we got closer to the comet. All of the colds and minor viruses they brought with them when they departed Earth have run their course by now.

“I’ve done a parasite inventory, and have found that more than three-quarters of the ambient pathogenic organisms have already gone extinct! It is time to release a new challenge.”

Saul sighed. “You’re the boss.” Actually, the entire bio committee was supposed to pass on immune challenges. But reminding Akio would only offend him. The procedure was routine, anyway.

Still, Saul’s nose already itched in unhappy anticipation.

He reached over to the bio-library console and punched out a rapid code. A page of data appeared in space before a black backdrop.

Saul nodded at the glowing green lettering. “There is a lovely array of nasty bugs at your disposal, Doctor. With what plague do you wish to infect your patients? We have chicken pox, fox pox, attenuated measles…

“Nothing so drastic.” Matsudo waved. “At least not so soon.”

“No? Well, then there’s impetigo, athlete’s foot… :’

“Amaterasu! Heaven forfend, Saul! In this dampness? Before the comet-tunnel habitats have been set up and the big dehumidifiers are working? You know how the navy feels about fungus aboard a spaceship. Cruz would have our—”

He stopped abruptly and grinned lopsidedly. “Ha ha. Very funny, Saul. You are pulling my leg, of course.”

Saul had known Matsudo casually, from scientific conferences and by reputation, for many years. But the man was still somewhat of an enigma to him. For instance, why had he volunteered to come on this mission? Of all the types who would sign up to leave Earth, spend seventy-three years of a seventy-eight-year mission in slot sleep, and return to a world grown alien and strange, which category applied to Akio? Was he an idealist, following Captain Miguel Cruz’s dream of what the mission might mean to mankind? Or was he an exile, like so many on this expedition?

Perhaps, like me, he’s a little of both.

Matsudo ran a hand through his lustrous black hair, as thick as any youth’s. “Just pick me out a head-cold virus, will you be so kind, Saul? Something that will challenge the crew enough to keep up their antibody production and T cell counts. They needn’t even notice it, for all I care.”

Saul spoke a chain of letters aloud, and a new page appeared. “The customer’s always right,” he ruminated aloud. “And you’re in luck! We seem to have eighty varieties of head cold on sale.”

“Surprise me;” Matsudo said. But then he frowned and held up both hands. “No! On second thought, let me choose! I don’t want any of your experimental monsters loose right now, no matter what you say about the wonders of symbiosis!”

Saul pushed off to one side as Akio bent forward to peer at the list of available diseases, muttering softly to himself. Obviously, Matsudo had left his contact lenses out again.

He’s about three decimeters taller than his grandfather, Saul thought. And yet he’s suspicious of change. A scientist, and yet he’s too conservative to get a corneal implant that would let him see without aid.

What ever happened to the innovative, future-hungry Japanese of so long ago?

For that matter, what had happened to Israel, his own homeland? How could the descendants of the Negev pioneers, the most potent warriors in two centuries, slowly decline into superstition and cultism? What had turned clear-eyed Sabras into cowed sheep who let the Levite and Salawite fanatics just walk in and take over?

The mysteries were part of a greater one that still amazed Saul, how courage seemed to be leaking away from humanity, even as the Hell Century was ending and better times appeared near at last.

It wasn’t a calming train of thought. Biological science was in just as bad shape. The bright hopes offered by Simon Percell and the genetic engineers of the early part of the century had nearly collapsed in a series of scandals more than a decade ago, leaving only a stolid pharmaceutical industry and a few mavericks such as Saul to carry on.

Earth was rapidly becoming unpleasant for mavericks—one of the reasons he was on this mission. Exile through space and time certainly beat some of the alternatives he had seen coming.

“We will use rhinovirus TR-3-APZX-471,” Matsudo announced, apparently satisfied with his selection. “Do you concur, Saul.”

Saul already felt a sneeze coming on. “A naive little varietal, but I’m sure you’ll be amused by its presumption.”

“I beg your pardon?”

“Never mind,” he grumped. “As official keeper of small animals, I’ll have an incubated vial of the nasty buggers in your in-box by tomorrow morning.” He touched a key and the glowing inventory disappeared.

Matsudo lifted himself easily in the one-eighth G of the Edmund’s laboratory wheel, and sat on the counter. He sighed, and Saul could tell that his friend was about to go philosophical on him. Over the long journey from Earth they had exchanged chess games and views of the world, and never budged each other on any issue at all.

“It’s not much like back when we were in Medical school, is it, Saul? You in Haifa and me in Tokyo ? We were brought up to hate pathogens—the infectious viruses and bacteria and prions—to want only to wipe them from the face of the Earth. Now, we culture and use them. They are our tools.”

Saul nodded. Today half a physician’s job involved careful application of those very horrors, serving them up judiciously to create challenges.

“Exercise the patient’s immune system, and let him do the rest,” Saul said, nodding. “It’s a better way, Akio. I only wish you’d see that my cyanutes are part of the same progression.”

Matsudo rolled his eyes. He and Saul had been over this many times.

“Again, I regret that I cannot agree. In one case we teach the body to be strong and reject that which is foreign. But you coax it to accept an interloper, forever!”

“Perhaps half of the cells in a human body are guest life forms, Akio… gut bacteria, follicle cleaners. They help us; we help them.”

Matsudo waved his hand. “Yes, yes. Most of what you call you, is not! I have heard it before. I know you see us not as individuals, Saul, but as great, synergistic hives of cooperating species.” There was a biting edge to Matsudo ’s voice that Saul did not remember having heard before. Exaggeration was not Matsudo ’s usual style.