Isaac Asimov - Fantastic Voyage II - Destination Brain

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"?

Very well, then. He had passed from desperately not wanting to attempt the project to a definite reluctance to abort it.

Dezhnev's voice broke in on his thoughts. "I don't think this little animal likes what's happening."

Morrison was conscious of a biting chill, and shivered as he became aware that the thin cotton uniform he wore was a totally inadequate shield against this sudden onset of winter.

And perhaps the white cell "thought" this, too, for the fog thinned and a rift appeared in it. Then, in another moment or two, the surroundings were clear and the white cell was a ball of fog to their rear, drifting away - or perhaps crawling away - amoebalike, from an unpleasant experience.

Boranova said (sounding a little dumbfounded), "Well, it's gone."

Dezhnev waved both hands high in the air. "A toast - if we had a small swallow of vodka with us - to our American hero. It was an excellent suggestion."

Kaliinin nodded at Morrison and smiled. "It was a good idea."

"As good as mine was bad," said Boranova, "but at least we know that your technique can do what it should, Sophia - as long as we know enough. And as for you, Arkady, ease the air-conditioning intensity before we all catch pneumonia. - So you see, Albert, we have already done well to take you with us."

"Perhaps," said Konev tightly, "but in the meanwhile, I think the white cell took us on an excursion. We are not where we were and I do not know exactly where we are."

Boranova's lips tightened and she asked with some difficulty, "How can you not know where we are? We were inside the white cell only a few minutes. It couldn't have moved us into the liver, could it?"

Konev seemed at least equally upset. "No, we're not in the liver, Madame." (He came down heavily on the honorific, giving it the French pronunciation.) "But I suspect the white cell, dragging us with it, has turned into a branching capillary so that we are now out of the mainstream of the arteriole - which was not yet quite a capillary - that we were carefully following."

"Which capillary did it turn into?" asked Boranova.

"That is what I don't know. There are a dozen capillaries it might have turned into and I don't know which one it was."

"Doesn't your red marker -" began Morrison.

"My red marker," said Konev at once, "works by dead reckoning. If I know where we are and the speed at which we're progressing, it will move along with us, turning when I tell it to turn."

"You mean," said Morrison incredulously, "it only marks your position insofar as you know your position - no more than that?"

"It is not a magical marker, no," said Konev freezingly. "It acts to mark our place and keep track of it, lest we lose it in the confusion of the three-dimensional complexity of the bloodstream and the neuronic networks, but we have to guide it. At this stage, it's not complex enough to guide itself. In an emergency, we can be located from outside, but that's a time-consuming process."

It seemed to be time for someone to ask a classically foolish question and that someone turned out to be Dezhnev. He said, "Why should the white cell have turned off into a capillary?"

Konev turned red. Speaking so rapidly that Morrison could hardly make out the Russian, he said, "And how should I know that? Am I privy to the thought processes of a white cell?"

"That's enough," said Morrison sharply. "We're not here to fight with each other." (He noted the quick look that Boranova had shot toward him and he chose to interpret it as representing gratitude.)

"Actually," he went on, "the solution is simple. We're in a capillary. Very well. The current is at a creeping pace in capillaries, so where is the difficulty in making use of the famous microfusion engines? If you put them into reverse, we will just back out of this capillary and eventually - not a very long eventually, either - we will be back at the junction point and in the arteriole again. Then we continue onward until we get to the proper turnoff and into the proper capillary. We'll have lost a little time and spent a little power, that's all."

Morrison's statement was greeted with solemn stares. Even Konev, who generally spoke - when he did - with his face steadfastly forward, turned now, his angry frown concentrated on Morrison.

Morrison said uneasily, "Why are you all looking at me like that? It's a perfectly natural course of procedure. If you had been driving a car and accidentally turned into a narrow alley and found it the wrong one, wouldn't you back out?"