Isaac Asimov - Fantastic Voyage II - Destination Brain

Morrison did so and, inevitably, pushed too hard against the back of the seat ahead. As a result of his insignificant inertia, he moved upward explosively and struck his head against the roof of the ship. Had this happened at the same speed under unminiaturized conditions, he might well have suffered the blinding pain of a concussion, but the very lack of mass and inertia that had sent him shooting upward had bounced him back almost once with no sensation of pain and virtually none of pressure. He was as easy to stop as he had been to start.

Konev clicked his tongue. "Gently. Just lift your hand upward edgewise, turn it slowly, then push it down flatwise, slowly. Do you get it?"

Morrison said, "I understand."

He followed Konev's suggestion and moved up slowly. He caught at Konev's shoulder and stopped himself.

Konev said, "Now, look here at the cerebrograph. Do you see where we are at this moment?"

Morrison found himself looking at an enormously complex network, with a distinct three-dimensional effect. It consisted of sinuous rills branching outward in such a way as to form an exceedingly intricate tree. In one of the larger branches there was a small red dot, moving slowly and progressively.

Morrison said, "Can you give me a broader view so that I can place this section?"

Konev, with another click of his tongue, one that might have signified impatience, expanded the view. "Does this help?"

"Yes, we're on the edge of the brain." He could recognize the individual convolutions and fissures. "Where do you plan to go?"

The picture magnified somewhat. Konev said, "We'll curve off here into the interior of the neuronic layer - the gray matter. And where I'd like to head for, by this route" - he named the areas in Russian rapidly and Morrison struggled to translate them in his mind into English - "is this area here which, if I have read your papers correctly, is a crucial node of the neuronic network."

"No two brains are exactly alike," said Morrison. "I can pin down nothing with certainty, all the more so if the particular brain in question is one I have never studied. Still, I would say the area you're heading for looks hopeful."

"Good, as far as that goes. And if we get to my destination, will you be able to tell more accurately whether we are at a crossroads where several branches of the network meet or, if not, in what direction and how far such a crossroads might be?"

"I can try," said Morrison cautiously, "but please remember that I have made no guarantees as to my abilities in this connection. I have not offered you any promises. I have not volunteered -"

"We know that, Albert," said Boranova. "We ask only that you do what you can."

"In any case," said Konev, "that's where we're going as a first approximation and we'll get there before long, even though the current is slowing. We are, after all, almost down to capillary size. - Strap yourself in, Albert. I'll let you know if I need you."

Morrison managed to operate the seat belt without any help, proving that even small triumphs can be sweet.

Almost to capillary size, he thought, and looked out through the walls of the ship.

The vessel wall was still at a comfortable distance, but it had changed in appearance. Earlier, the steadily pulsating walls had been rather featureless. Now, however, Morrison could make out no pulsing and the walls were beginning to look faintly tiled. The tiling, Morrison realized, consisted of the cells that made up the thinning walls.

He could not actually get a clear look at the tiling, either, for the red corpuscles were in the way. They were now soft bags nearly the size of the ship. Occasionally, one ballooned past the ship at close quarters and was pushed elastically inward at the point of contact, without undergoing any visible harm.

One time a small smear was left behind. Perhaps the contact had been just a little too forceful and a line of miniaturized molecules had been formed against the hull, Morrison thought. The smear lifted off quickly, however, and dissolved in the surrounding fluid.

The platelets were another story, since by their very nature they were much more fragile than the red corpuscles.

One made a head-on collision with the ship. Or perhaps it had been slowed by a collision with a red corpuscle so that the ship had overtaken it. The prow of the ship penetrated deeply and the skin of the platelet punctured. Its contents oozed out slowly, mixing with the plasma and then forming into two or three long strings that tangled with each other. They clung to a portion of the ship's hull for quite a time, trailing behind.

Morrison waited to see any evidence of a clot forming. None did.

Minutes later Morrison saw, up ahead, a milky fog that seemed to fill the blood vessel from wall to wall, pulsating and undulating. Inside it were dark granules that moved steadily from one side to the other. To Morrison, it looked like a malignant monster and he couldn't help but cry aloud in a moment of terror.

Dezhnev turned his head, startled, and said, "It's a white cell, Albert, a leucocyte. It is nothing to be bothered about."

Morrison swallowed and felt distinctly annoyed. "I know it's a white cell. It just caught me by surprise. It's bigger than I thought it would be."

"It's nothing," said Dezhnev. "A piece of pumpernickel, really, and no bigger than it should be. We're just smaller. And even if it were as big as Moscow, so what? It's just floating along in the bloodstream as we are."

"As a matter of fact," said Kaliinin gently, "it doesn't even know we're here - I mean, that we're anything special. It thinks we're a red corpuscle."

Konev seemed to be addressing the air in front of him in an abstracted sort of way, saying, "White cells do not think."

A flash of resentment crossed Kaliinin's face, flushing it slightly, but her voice remained even. "By saying 'think,' Albert, I am merely using a figure of speech. What I mean is that the white cell's behavior toward us is that which it would display toward a red corpuscle."

Morrison cast another look toward the large billowing cell up ahead and decided that, harmless or not, he found its appearance distasteful. He looked with much appreciation at the contrast made by Kaliinin's pretty high-cheekboned face, and wondered why she had never had that little mole under the left corner of her lip removed. Then he wondered if it didn't add just the right trifle of piquancy to a face that might otherwise be considered too pretty to possess character.

That moment of beside-the-point speculation effectively removed the uneasiness that the white cell's appearance had introduced and Morrison returned, in his mind, to Kaliinin's statement.

"Does it act as though we're a red corpuscle because we're the right size for it?"

"That may help," said Kaliinin, "but it's not the real reason. You judge a red corpuscle to be a red corpuscle because you see it. The white cell judges a red corpuscle to be one because it senses the characteristic pattern of the electromagnetic pattern on its surface. White cells are trained - that is just another figure of speech - let us say, adapted - to ignore that."

"But this ship doesn't have the electromagnetic pattern of a red corpuscle… Ah, but I guess you've taken care of that."

Kaliinin smiled in gentle self-satisfaction. "Yes, I have. It is my speciality."

Dezhnev said, "That is it, Albert. Our little Sophia knows, completely in her head" - he tapped his right temple - "the exact electromagnetic pattern of every cell, every bacterium, every virus, every protein molecule, every -"

"Not quite," said Kaliinin, "but those I forget, my computer can supply. And I have a device here that can use the energy of the microfusion motors to place positive and negative electric charges on the ship in whatever pattern I choose. The ship has the charge pattern of a red corpuscle on itself as best as I can duplicate it, and that is close enough to cause the white cell to react - or, rather, not to react - accordingly."