"I agree," said Dezhnev boisterously. "This has been a remarkably uneventful trip so far."

"That's the best kind, I should think," said Morrison.

But Dezhnev held up a disapproving hand. "My old father used to say: 'To want peace and quiet above all else is to hope for death.'"

"Go ahead, Sophia," Boranova said firmly. "We waste time."

Kaliinin hesitated a bare moment - the time required, perhaps, to remember that Boranova was captain of the ship - then her hand flickered over the controls of her device and the configurations upon the television screen altered markedly. (Morrison admired, in an apprehensive sort of way, the speed with which she did it.)

Morrison lifted his eyes to the white cell ahead, and for a moment he saw no change. And then it seemed as though a fit of trembling overtook the monster and Dezhnev whispered, "Aha, it recognizes the presence of its prey."

At the extreme forward end of the white cell, its substance seemed to bulge toward and all around them in an uneven circle. At the same time, the substance in the center retreated as though it were being sucked in. Morrison envisioned a monster's jaws preparing for a meal.

Konev said, "It works, Natalya. That creature ahead is preparing to envelop and engulf us."

Boranova said, "So it is. Very well, Sophia, restore us to the red cell mode."

Again Kaliinin's fingers flickered and the configurations on the screen returned (as nearly as Morrison's memory could judge) to what they had earlier been.

This time, however, the white cell remained unaffected. Its outer rim was shooting past the ship, which was now heading into the deep central concavity.

Morrison was appalled. The entire ship was encased by something that looked precisely like fog - a gritty granular fog, within which a multilobed object, faintly denser than the rest, writhed its way around them. Morrison knew that this must be the nucleus of the white cell.

Konev snapped out angrily, "Apparently, once the white cell gears itself for engulfment, the rest is automatic and nothing will stop it. - What now, Natalya?"

Boranova replied quietly, "I admit I hadn't expected this. The fault is mine."

"What's the difference?" said Dezhnev, frowning. "It's no matter. What can this blob do to us? It cannot crush us. It is not a boa constrictor."

Konev said, "It can try to digest us. We're in a food vacuole right now and digestive enzymes are pouring in around us."

"Let them pour," said Dezhnev. "I wish them the joy of the attempt. The ship's wall is not digestible to anything a white cell has. After a while, it will reject us as indigestible residue."

"How will it know?" asked Kaliinin.

"How will it know what?" snapped Dezhnev.

"How will it know we are indigestible residue? It was spurred into activity by our bacterial charge pattern."

"Which you removed."

"Yes, but as someone remarked, the white cell, once stimulated, apparently has to go through its whole cycle of activity. It is not a thinking device; it is entirely automatic." Kaliinin was frowning now and looking around at the others. "It seems to me that the white cell will continue trying to digest us until it is given the appropriate stimulus that will put its engulfment mechanism into reverse and allow it to eject us."

Boranova said, "But we now have the charge pattern of a red corpuscle again. Don't you think that would stimulate rejection? It doesn't eat red cells."

"I think it's too late for that," said Kaliinin a little diffidently, as though nervous about standing up to Boranova. "The red corpuscle pattern keeps it unengulfed, but once it is engulfed by some means, it would seem that the pattern alone is insufficient to spark ejection. After all, here we are; we are not being ejected."

Her eyes - all five pairs of eyes, in fact - uneasily surveyed the wall of the ship. They were trapped in the cloudy cell.

"I think," Kaliinin went on, "that there's a charge pattern to the kind of indigestible residue left by the bacteria the white cell is designed to engulf and that that alone would be a trigger for ejection."

"In that case," said Dezhnev, "give it the pattern it wants, Sophia, my little chicken."

"Gladly," said Kaliinin, "if you will tell me what it is because I don't know. I can't just try patterns at random. The number of possible patterns is astronomical."

"As a matter of fact," said Konev, "can we be sure the white cell ejects anything at all? Perhaps indigestible residue becomes part of its granular material and remains within it until it is removed and dismantled in the spleen."

Boranova said sharply (perhaps weighed down with the knowledge that she was responsible for their present situation, thought Morrison), "There is no point in babbling. Is there a constructive suggestion?"

Dezhnev said, "I can turn on the microfusion motors and bore a way out of the white cell."

"No," said Boranova sharply. "Do you know the direction which we are heading at this moment? Inside this food vacuole we may be slowly turning or the vacuole itself may be drifting through the cell's substance. If you smash your way outward, you may damage the wall of the blood vessel and the brain itself."

Konev said, "For that matter, white cells can wiggle out of a capillary, working their way between the cells that make up the capillary wall. Since the path we have taken has led us into an arteriole branch that has narrowed to just about capillary size, we can't even be sure that we're still in the bloodstream."

"Yes, we can," said Morrison suddenly. "The white cell can pinch itself small, but it can't pinch us small. If it squeezes out of the vessel, it would be forced to leave us behind. - And that would be a good thing, except that it hasn't done it."

"There you are," said Dezhnev. "I should have thought of it sooner. Natasha, make us bigger and crack the white cell open. Give it indigestion like it has never had."

Again a sharp negative from Boranova. "And crack the blood vessel open, too? The blood vessel is fairly small now, not much wider than the white cell."

Kaliinin said, "If Arkady will get in touch with the Grotto, someone there might have an idea."

There was silence for a moment and then Boranova said in a half-strangled way, "Not just yet. We have done something foolish - well, I have - and you know as well as I do that it would be better for all of us if we didn't need help."

"We can't wait forever," said Konev restlessly. "The fact is that I don't know where we are by now. I can't rely on the white cell drifting with the bloodstream or with maintaining any given speed, for that matter. Once we are lost, it may take considerable time to locate ourselves and we may need help from the Grotto to do it, too. In that case, how do we explain being lost?"

Morrison said, "How about the air-conditioning?"

There was a pause and Boranova said, "What do you mean, Albert?"

"Well, we're sending miniaturized subatomic particles out of the ship and into interplanetary space. They carry heat away from the ship, I was told, so that we remain cool even in the all-pervasive warmth of the body we're in. That coolness must be something the white cell is not designed to tolerate. If we turn up the air-conditioning and become colder still, there may come a time when the white cell will be uncomfortable enough to eject us."

Boranova mulled this over and said evenly, "I think - possibly - that might work."

Dezhnev said, "Don't bother thinking. I've turned up the air-conditioning to maximum. Let's see if anything happens besides all of us getting frostbite."

Morrison watched the fog outside. He was well aware that he was as tense as the others. He was not in agony over an unfortunate decision - an ill-advised experiment. Nor was he biting his nails over the fate of Shapirov and yet - Tapping his own emotions, it occurred to him that having come thus far, having been miniaturized and finding himself in a small cerebral arteriole, he suddenly had an urge to check out his theories. Had he come this far in order to turn back and spend the rest of his life, holding up an imaginary thumb and forefinger nearly in contact and saying in the depth of his mind, "Missed it by that much"?