Isaac Asimov - Fantastic Voyage II - Destination Brain

"When did you do that, Sophia?" asked Morrison with interest.

"When we were reduced to the size that would make us a potential object of interest for a white cell or for the immune apparatus generally. We don't want antibodies swarming over us, either."

A thought occurred to Morrison. "Since we're talking about being reduced in size, why hasn't the Brownian motion gotten worse? I should think it would batter us more as we got smaller."

Boranova put in from behind, "So it would if we were unminiaturized objects of this size. Since we are miniaturized, there are theoretical reasons that prevent Brownian motion from getting very bad. It's nothing to worry about."

Morrison thought about it, then shrugged. They weren't going to tell him anything they thought might make him too knowledgeable in the matter of miniaturization and what did that matter? The Brownian motion had not grown worse. In fact, it had grown less troublesome (or was he just getting used to it?) and he had no objection to that. That made it, as Boranova said, nothing to worry about.

His attention shifted back toward Kabinin. "How long have you been training in this field, Sophia?"

"Since my graduate days. Even without Shapirov's coma, we all knew the time would come when a trip through a bloodstream would become necessary. We've been planning something like this for a long time and we knew that this skill of mine would be needed."

"You might have planned an automated crewless ship."

"Someday, perhaps," said Boranova, "we will, but not yet. We cannot, even now, make the automation equivalent to the versatility and ingenuity of a human brain."

"That's true," said Kaliinin. "An automated pattern maker would place us in the red corpuscle pattern as a way of following the path of least resistance, and it would do little more than that. After all, it would be a useless expense and perhaps an impractical exercise altogether to try to instil in an automated pattern maker the ability to change appropriately in response to all sorts of improbable conditions. When I am present, however, I have the capacity to do almost anything. I can change the pattern to meet an unlikely emergency, to test the value of something earlier unthought of, or simply to suit a whim. - For instance, I could change the ship's pattern to that of an E coli bacterium and the white cell would attack at once."

"I'm sure of that," said Morrison, "but don't do it, please."

"No fear," said Kaliinin. "I won't."

But Boranova's voice sounded in sudden - and uncharacteristic - excitement. "On the contrary, Sophia, do that!"

"But, Natalya -"

"I mean it, Sophia. Do it. We haven't tested your instrument under field conditions, you know. Let's try it."

Konev muttered, "That's a waste of time, Natalya. Let us first get to where we're going."

Boranova said, "It won't do us any good to get there - if we can't enter a cell. Here is an immediate opportunity at hand to see if Sophia can control the behavior of a cell."

"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?"