by Isaac Asimov
Dezhnev's smile became an uncomfortable one and his somewhat yellow upper incisors caught at his lower lip.
Boranova said in her masterful contralto, cutting off any retort Dezhnev might have made, "And Shapirov. What of him?"
"That," said Dezhnev, "has passed. An injection of some sort steadied the heartbeat."
Konev said, "Well, then, are we ready to go?"
"Yes," said Boranova.
"In that case - out of the bloodstream at last."
51.
Boranova and Kaliinin were bent over their instruments. Morrison watched them for a few moments, but, of course, knew nothing of what was going on. He turned to Dezhnev, who sat in a relaxed position (unlike Konev, whose body was tense, almost ridged with muscle), and said, "What will be done, Arkady? We can't very well just blast our way out of a blood vessel in the brain."
"We'll sneak out once we're small enough. We're miniaturizing again. Look around you."
Startled, Morrison did. He realized that every time the outside world seemed to stabilize, he quickly learned to take it for granted and to pay no attention to it.
The current had picked up speed. Or, rather, it hadn't, but the ship had shrunk in size once more and objects moving by took correspondingly less time to pass, so that the mind, insisting on considering the ship's size unchanged, interpreted what was seen as a faster current.
A red cell passed by, moving as it had (or seeming to move as it had) in the carotid artery, but despite its speed, it billowed past for a long time, like a quivering whale passing a rowboat. It had grown faint indeed. It was almost transparent now and its edge was fuzzy with Brownian motion. There was a grayish dimness about it, so that it looked like an angry thundercloud spreading its way over the heavens. It had lost most of its oxygen by this time, of course, giving it up to the avid brain cells which, without motion or visible signs of life, consumed one quarter of all the oxygen carried by the blood to the various organs of the body. For all that the brain seemed to simply sit there, sense perception, response, and thought, all of it coordinated with a complexity that no human computer could come within an astronomical distance of duplication - might never duplicate - did not come cheap.
To make up for the spreading of the red cells, the platelets, and the comparatively rare white cells that had grown into monsters that were now too large to grasp, the blood plasma was becoming far less featurelessly liquid.
It had started to turn grainy and now the grains were slowly expanding as they shot past with gradually increasing speed. Morrison knew he was looking at protein molecules and, after a while, it seemed to him that through their whirling and flexing he could make out the helical arrangements of their atoms in fuzzy manner. Some had a miniature forest of lipid molecules partially encasing them.
He was becoming aware also of movement, not the tremble of Brownian motion but a lurching that was becoming more pronounced.
He turned his head to look out the other side at the capillary wall to which they were attached.
The tiling was gone - or at least one tile (or cell, as he might as well think of it now) had expanded to the point where it was the only one to be seen. Slipping off behind was the bulge of the nucleus of the cell, large and thick and growing larger and thicker.
The ship lurched as part of it slid away from the wall and then lurched again as it slid back.
"What's happening?" said Morrison, looking at Kaliinin, who shook her head impatiently. She was totally absorbed in her work.
Dezhnev said, "Sophia is trying to neutralize the ship's electric charge here and there so that it lets go before the tension damages the wall. And she has to find new areas of attachment to keep from losing the wall altogether. It's not easy, having to miniaturize and, at the same time, staying attached to the wall."
Morrison said, alarmed, "How far will we miniaturize?"
His words were overborne by Kaliinin's shrill command. "Arkady, move it forward. Gently! Just put forward pressure on the ship."
"Yes, Sophia - but tell me when to stop." To Morrison, he added, "My father used to say: 'Between not enough and too much is a hair's breadth.'"
"More, more," said Kaliinin. "All right. Now we'll try." The ship seemed to stick and strain and then it suddenly slid forward and Morrison felt himself thrust gently back against his seat.
"Good," said Kaliinin. "Just a little less now."
The cell came to an end. Beyond it was another cell. Thin cells, as cells went, a mere film of cells, fitted together to make a tiny tube, with the ship and its crew of five clinging to the inner surface by minute attractions of electric charge.
The space between the adjoining cells seemed ropy, with cables stretching from inside one cell to the other. They were not all intact and there were stumps visible like the remains of a felled forest. It seemed to Morrison that there were narrow gaps in that felled forest, but he couldn't see clearly from the angle at which he viewed them.
He said again, "How far will we miniaturize, Arkady?"
"Eventually to the size of a small organic molecule."
"But what would the chances be of spontaneous deminiaturization at that size?"
"Appreciable," said Dezhnev. "Much more than it was when we were the size of a red corpuscle or even of a blood platelet."
"Still not enough to worry about," said Boranova. "I assure you."
"Exactly," said Dezhnev and raised his hand slightly with the first two fingers crossed so that Morrison could just see it and Boranova, farther back, could not. That American gesture had become universal and Morrison, knowing exactly what it meant, felt himself growing cold inside.
Dezhnev was looking straight ahead, but he might have sensed Morrison's grimace or heard his soft grunt. He said, "Don't worry about it, young Albert. It is always wise to have but one worry at a time and right now let us worry about squeezing out of the blood vessel. - Sophia, my loved one."
"Yes, Arkady," she said.
"Weaken the field in the rear of the ship and when I move grope for one ahead."
"I will do so, Arkady. Didn't your father once say: 'There is no point in trying to teach a thief to steal'?"
"Yes, he did. Steal, then, little thief, steal."
Morrison wondered whether Dezhnev and Kaliinin were deliberately being lighthearted in the face of the possibility of sudden death as a way of cheering him up? Or were they showing contempt for his cowardice? He chose the former. Surely when an action might equally well be interpreted as friendly or hostile, one might as well choose the friendly. Perhaps Dezhnev's father would have agreed. With that thought, he felt cheered.
The ship's rear seemed to be hanging loosely and to remain several centimeters (several picometers in real measure?) from the wall of the capillary. Morrison studied it closely and could see the serried ranks of protein and lipid molecules that made up that wall.
He thought, What are we doing ignoring this? Here is our opportunity to study tissues with greater precision than the best scanning electron microscope can - and to study them while alive; to see not only position but living change and motion. We have passed through the bloodstream and narrowed in on a capillary wall without looking at anything in any real scientific sense. We are only passing through, with no more interest than we would show if we were in a subway, barreling through an underground tunnel. - All to study oscillations that might be produced by thought… and might not.
The ship was inching along (an old word, thought Morrison suddenly, antedating the metric system, but he'd never heard anyone say "centimetering along") as though it were somehow feeling its way. Perhaps, between Dezhnev's motors and Kaliinin's flickering electric fields, that was precisely what it was doing.
"We're approaching the junction, little Sophia," said Dezhnev in a curiously tight voice. "Make sure your hold is firm in front, while I move forward another meter or so."
"I suspect from the appearance and electrical behavior," said Kaliinin, "that we have a clump of arginines toward the junctio
n. That represents a strong region of positive charge and I can handle that as smoothly as sour cream."
But Boranova said sternly, "No overconfidence, Sophia. Keep a firm watch. If you miss and the ship tears loose, there will be much to do over."
"Yes, Natalya," said Sophia, "but with all respect, the warning is not really needed."
Dezhnev said, "Sophia, do exactly what I say. Keep only the prow of the ship attached to the wall, but strongly. Release everything else."
"Done," said Sophia faintly.
Morrison found himself holding his breath. The rear of the ship had spun away from the wall, but it held in front. The bloodstream caught the detached rear end and pushed the ship into a position at right angles to the current, while the capillary wall, where the ship still held, moved outward like a pimple.
Morrison said tightly, "Watch out. We'll pull a section out of the wall."
"Quiet, all!" thundered Dezhnev. Then, in an ordinary voice, "Sophia, I shall increase the engine push slowly. Get yourself in position to break all remaining attraction. The ship is to be entirely neutral - but not until I say so."
Sophia cast a quick look toward Boranova, who said in her quiet way, "Do exactly as you're told, Sophia. For this, Arkady's word is absolute."
Morrison imagined he felt the ship straining forward. The section of the capillary wall to which it was attached stretched farther and farther.
Sophia said urgently, "Arkady, either the field will snap or the wall will."
"Another moment, dear one, another moment. - Now."
The wall snapped back and the ship bounded forward in a great leap that rocked Morrison gently backward. The forward end of the ship buried itself in the cement stuff between the two cells of the capillary wall.
52.
For the first time, Morrison was aware of the laboring of the microfusion engines. There was a subliminal throbbing as the ship worked its way through the joint with what seemed increasing difficulty. There was nothing to see up ahead. The thickness of the capillary wall, very thin though it was in normal terms, was far thicker than the length of the ship.
The ship was now totally immersed in the joint and Dezhnev, beads of sweat on his forehead, turned his head and spoke to Boranova. "We're using up energy faster than we should."
Boranova said, "Then stop the ship and let's consider."
Deshnev said, "If I do that, there is a chance that the natural elasticity of this material will pop us out of the joint and back into the bloodstream."
"Slow the engines down, then. Choose a level that will be enough to keep us in place."
The throbbing came to an end.
Dezhnev said, "The joint is exerting considerable pressure on the ship."
"Enough to crush us, Arkady?"
"Not now. But who can say for the future if the pressure continues."
Morrison burst out. "This is ridiculous. Didn't someone say we're the size of a small organic molecule?"
"We're the size of a glucose molecule," said Boranova, "which is made up of twenty-four atoms altogether."
"Thank you," said Morrison freezingly, "but I know how many atoms there are in a glucose molecule. As it happens, small molecules drift through the capillary walls constantly by diffusion. Diffusion! That's the way the body works. Why aren't we diffusing through?"
Boranova said, "Diffusion is a statistical proposition. There are twenty-four billion trillion glucose molecules in the bloodstream at any given time. They move around randomly and some manage to hit in such places and in such ways as to move through a joint, or to move into the membrane of a capillary wall cell, into the cell, and out the other side. A very small percentage succeed at any given second, but that is enough to ensure proper tissue functioning. However, by chance, a particular glucose molecule may remain in the bloodstream for a month without diffusing. Can we wait a month for a chance to do its work?"
"That's no argument, Natalya," said Morrison impatiently. "Why don't we simply do deliberately what a real glucose molecule would do by chance? Especially now, when we're part way through the joint. Why are we stuck in position?"
Konev said, "I'm on Albert's side. Diffusion probably isn't a passive leakage. There's some sort of interaction between the diffusing object and the barrier through which the diffusion takes place - except that no one knows what the interaction might be exactly. Especially here, where we face the blood-brain barrier."
"We're here at the barrier," said Dezhnev. "You're the brain expert. Can you look around and tell us how this diffusion works?"
"No, I can't. But glucose is one molecule that gets through the blood-brain barrier easily. It must because it is the brain's sole fuel for energy. The trouble is that while the ship is as small as a glucose molecule, it isn't a glucose molecule."
"Are you getting at something, Yuri," said Boranova, "or is this a lecture?"
"I'm getting at something. We had the ship become uncharged in order to lunge into the joint, but why leave it uncharged now? Can it be given the charge pattern of a glucose molecule? If so, it will be a glucose molecule as far as Shapirov's body is concerned. I suggest you order it done, Natalya."
Kaliinin did not wait for the order. She said, "It is done, Natalya."
(They each addressed Boranova, Morrison noted. Each still maintained the fiction of the other's nonexistence.)
Dezhnev said, "And the joint's pressure decreases at once. It recognizes a friend, so it bows politely and steps aside. My father's mother, long may I keep her memory, would have cried out, 'Black magic,' and at once would have hidden beneath the bed."
"Arkady," said Boranova, "increase the power of the engines and pass through before the joint notices that underneath the glucose pattern is something that is not glucose."
"Yes, Natalya," said Dezhnev.
Morrison said, "This one is yours, Yuri. Your suggestion was just right. In hindsight I see that I should have thought of that, too, but the fact is, I didn't."
Konev said gruffly, as though finding praise something he couldn't handle, "It was nothing. Since the brain lives on glucose, we got down to glucose size. Eventually, we would have had to have a glucose pattern, and as soon as you asked the question why we weren't diffusing when we should have been, I realized we needed the pattern already."
Dezhnev said, "Members of the expedition, we are through the joint. We are out of the bloodstream. We are in the brain."
53.
In the brain, thought Morrison, but not in a brain cell. So far they had only passed from the intercellular space between the cells of the capillary wall, into the intercellular spaces of the brain where the support structures existed that maintained the form and interrelationships of the nerve cells, or neurons. Remove them and the cells would squash into amorphous masses, pulled together by gravity and unable to maintain any sensible function.
It was a jungle, made up of thick viny threads of collagen. (This was the nearly universal animal connective protein that fulfilled the function of cellulose in plants, less cheaply, since it was protein rather than carbohydrate, but far more flexibly.) Through the eye of ultraminiaturization, those collagen threads, totally invisible without an electron microscope, looked like tree trunks, leaning this way and that in a world in which gravity was of little importance.
There were finer and still finer threads. Morrison knew that some of them might be elastin and that the collagen itself might come in subtly different varieties. If he could see the whole in a wider view, from a less-miniaturized standpoint, he would have been able to detect order and structure. At this level, however, it was chaotic. One couldn't even see far in any direction; the overlapping fibers blocked vision.
Morrison became aware that the ship was moving very slowly. The four others were each staring around in wonder. Either they had not expected this (Morrison hadn't, for he had been too interested in the electrical properties of the brain to think much concerning its microanatomy) or, if they had, they had nevertheless failed to visualize it.
Morrison said, "How do you expect to find your way to a neuron? Does anybody know?"
Dezhnev was the first to answer, "The ship can only move straight ahead, so we move straight ahead until we get to a cell."
"How do we move straight ahead through this jungle? If we can't steer the ship, how do we move around obstacles?"
Dezhnev rubbed his chin thoughtfully. "We don't move around, we push around. The ship will move past one of those objects and there will be more friction on the contact side than on the other, so our path bends, like a comet rounding the sun." He smiled. "Cosmonauts do that when they use gravity to skim around a satellite or planet. We'll do it to skim around those things."
Konev said morosely, "Those things are collagen fibers."
Morrison said, "Some of them are pretty thick. You won't always pass by. You'll hit one head-on and stay there and if you can only move forward, what will you do? This ship was designed only for the bloodstream. We're helpless out of it with nothing to carry us along."
Boranova interposed. "Arkady, you have three microfusion engines and the jets, I know, are arranged at the rear at the apices of an equilateral triangle. Can you fire only one of them?"
"No. One contact controls all three."
"Yes, Arkady, that is how it is now. But you designed the ship and you know the details of its controls. Is there anything you can do to modify them so that you can fire them one at a time?"
Dezhnev took a deep breath. "Everyone told me over and over again that I must cut corners, that I must save the budget, that I must do nothing to irritate the bureaucrats."
"Aside from that, Arkady, is there anything you can do?"
"Let me think. It means jury-rigging. It means finding something to make switches out of, and extra wire, and who knows if it will work or how long it will work if it does, and if we won't end up worse than we are. I see what you mean, though. If I can fire only one of the engines, it will set up an unbalanced thrust."
"You'll be able to steer then, depending on which you fire."
