The wall that says "Welcome, stranger" has never been built.

55.

Boranova's nostrils flared slightly and her dark eyebrows hunched together, but her voice remained calm.

"Arkady," she said, "You will travel forward in as straight a line as possible. Curve to a minimum extent and, if you can, curve left and right alternately. And, since we're in a three-dimensional situation, up and down alternately."

"It would get confusing, Natasha," said Dezhnev.

"Of course it will, but perhaps it won't get completely confusing. We may not be able to travel ruler-straight, but maybe we won't go in circles, spirals, or helixes either. And sooner or later we should reach a cell."

"Perhaps," said Dezhnev, "if you deminiaturize the ship a little bit -"

"No," said Boranova.

"Wait, Natasha. Think about it. If we deminiaturize a bit, then there will be less space to travel. We grow larger, the space between blood vessel and neuron grows smaller." He made eloquent gestures with his hands. "You understand?"

"I understand. But the larger we get, Arkady, the more difficult it will be to pass between the fibers. The neurons of the brain are well-protected. The brain is the only organ to be completely encased in bone and the neurons themselves, which are the most irregular in the body, are well-packed with intercellular material. Look for yourself. It's only if we're down to the size of a glucose molecule that we can make our way through and around the collagen without, perhaps, doing drastic damage to the brain."

At this point, Konev committed the unusual act of turning in his seat, looking upward as he turned to his left so that his glance passed over Kaliinin before meeting Boranova's eyes. He said, "I don't think we have to travel onward completely blind - completely at random."

"How otherwise, Yuri?" asked Boranova.

"Surely the neurons give themselves away. Each has nerve impulses running its length periodically and at very short intervals. That might be detected."

Morrison frowned. "The neurons are insulated."

"The axons are - not the cell bodies."

"But it is the axons where the nerve impulse is strongest."

"No, it is the synapses where the nerve impulse may be strongest and they are not insulated, either. The synpases ought to be sparking all the time and you ought to be able to detect it."

Morrison said, "We couldn't in the capillary."

"We were on the wrong side of the capillary wall at the time. - Look, Albert, why are you arguing the matter? I'm asking you to try to detect brain waves. That's why you're here, isn't it?"

"I was kidnapped," said Morrison violently. "That's why I'm here."

Boranova leaned forward. "Albert, whatever the reason, you're here and Yuri's suggestion is a reasonable one. - And, Yuri, must you always be confrontational?"

Morrison found himself shaking with anger and for a moment he wasn't sure why. Konev's suggestion was indeed reasonable.

Then it occurred to him that he was being asked to put his theories to the test under conditions which would allow him no escape. He was on the very border of a brain cell that was magnified with respect to himself to mountainous proportions. He might be asked next to make his test inside, actually inside, such a cell. And if he did - and if he failed - under what blanket of argument and excuse could he hide from the fact that his work was wrong and had always been wrong?

He was angry, surely, at being thrust into this uncomfortable corner by circumstance and not at Konev particularly.

He was aware of Boranova waiting for him to say something and of Konev maintaining his incandescent stare.

Morrison said, "If I detect signals, I will detect them from all sides. Except for the capillary we have just left, we're surrounded by uncounted numbers of neurons."

"But some are closer than others," said Konev, "and one or two would be closest of all. Can't you detect the direction from which the signals will be the strongest? We can home in on that signal."

"My receiving device isn't equipped to determine directional signals."

"Ah! Then Americans, too, make use of devices that are equipped for specific purposes and do not prepare for emergency needs. It is not merely the ignorant Soviets who -"

"Yuri!" said Boranova sternly.

Konev swallowed. "I suppose you'll tell me I'm confrontational again. In that case, Natalya, you tell him to think of a way of devising something that will tell him the direction from which the strongest signals are coming."

"Please, Albert, make the attempt," said Boranova. "If you fail, we shall just have to blunder our way through this collagen jungle and hope we come upon something before too long."

"We're blundering onward even as we speak," put in Dezhnev almost cheerfully, "but I still see nothing."

Still angry, Morrison activated his computer and put it into the brain wave reception mode. The screen flickered, but it was only noise - though the noise was more prominent than it had been within the capillary.

Until now, he had always used leads that involved micropositioning inside a nerve. Where was he to put the leads now? He had no nerve to put them into - or, rather, he was already inside the brain, which made the whole matter of positioning anomalous. Perhaps, though, if he let the leads (made as stiff as possible) rise in the air and spread apart like a pair of antennae, they might play the part. At their present size, the spread would be tiny and could scarcely be useful but -

He doubled and redoubled the leads and they stood up in long loops, looking very much like the insect antennae that had first given them their names. He then focused and sharpened reception as well as he could and the flickering on the screen suddenly broke into deep narrow waves - but only for a moment. Involuntarily, he let out a cry.

"What happened?" said Boranova, startled.

"I received something. Just a flash. But it's gone."

"Try again."

Morrison looked up. "Listen. All of you. Quiet. Working this thing is difficult and I manage best when I can concentrate entirely. Understood? No noise. Nothing."

"What was it you received?" said Konev softly.

"What?"

"Like a flash. You received something like a flash. May we know what it was?"

"No. I don't know what I received. I want to listen again." He looked behind him to the left. "Natalya, I'm in no position to give orders, but you are. I am not to be disturbed by anyone, particularly by Yuri."

"We will all be quiet," said Boranova. "Proceed, Albert. - Yuri, not one word."

Morrison looked sharply to his left, for there had been a soft touch on his hand. Kaliinin was looking at him keenly and there was a small smile on her face. She mouthed words in an exaggerated fashion and he managed to catch the Russian: "Pay no attention to him. Show him! Show him!"

Her eyes seemed to glitter. Morrison could not help but smile warmly in response. She might be motivated entirely by a desire for vengeance against the man who had abandoned her, but he enjoyed the look of assurance and faith that was present in her eyes.

(How long ago had it been since a woman had looked at him with pride and with trust in his abilities? How many years ago had it been since Brenda had lost hers?)

A spasm of self-pity shook him and he had to wait for a moment.

Back to the device. He tried to shut out the world, shut out his condition, think only of his computer, only of the tiny fluctuations in the electromagnetic field produced by the interchange of sodium and potassium ions across the neuronic membrane.

The screen flashed again, steadied, and resolved into a pattern of low peaks and valleys. Carefully, barely daring to touch the keys, Morrison threw in an expansion directive. The peaks and valleys spread out, the edges sliding off the screen. On the single peak and valley left remaining, there was a fuzzy smaller wiggle.

It's recording the waves, he thought, afraid to say so, afraid even to think it with any intensity, lest the slightest physical or mental effect suffice to blank it out.

The minor wiggle - the skeptic waves, as he called them - went out of focus and back in, never quite sharpening.

Morrison wasn't surprised. He might be detecting the fields of a number of cells that didn't quite duplicate each other. There was also the insulating effect of the plastic wall of the ship. There was the eternal shaking of Brownian motion. There might even be the interfering charge of atom groupings outside the miniaturization field.

The wonder was that he had gotten waves at all.

Slowly he made hand contact with the antennae - slid his fingers up and down, first one hand, then the other, then both in unison, then both in opposite directions. Then he bent the antennae gently, this way and that. There were sharpening and fuzzing of the skeptic waves, but he didn't know, for certain, exactly what he was doing that resulted in the sharpening.

And then, at a certain point, the tiny waves sharpened acutely. A little to one direction and another they fuzzed, but in one particular direction they were sharp. He tried to keep his hands from trembling.

"Arkady," he said.

"Yes, my American magician," said Dezhnev.

"Curve left and a little upward. I don't want to talk too much."

"I'll have to curve around the fibers."

"Curve slowly. Too fast and I'll lose the focus."

Morrison fought to keep his eyes from flickering leftward toward Kaliinin. Just one look at her face and one inevitable thought of her prettiness would be distraction enough to fuzz out the screen. Even the thought of distraction was itself distracting enough for the thought wave to flicker.

Dezhnev was curving the ship in the gentle arc that was all that the offset motors would manage and slowly Morrison shifted the antennae to suit. Occasionally he muttered a brief whispered direction: "Up and right," "Down," "A little left."

Finally he gasped, "Straight ahead."

It should get easier, he thought, as they got closer, but he couldn't relax until a neuron was actually in sight. And, through the obscuring collagen thicket, that was not likely to be until they were nearly on top of it.

Concentrating on only one subject was as tiring as clenching a muscle and leaving it clenched. He had to introduce just a bit of quick variation. He had to think of something else, but something neutral, something that would, for a while, leave his mind unclenched. So he thought of his broken family because he had thought of them so often that the image had faded and lost effect somehow. It was a photograph that was growing bent and gray and he could snap out of it quickly and return to the single-minded contemplation of the skeptic waves.

Then - without warning and overwhelmingly - another thought invaded his mind. It was a sharp mental picture of Sophia Kaliinin, looking younger, prettier, and happier than she had ever seemed to him in the short time he had known her. And with that picture came a tumbling of love and frustration and jealousy that left him weak.

He had not been consciously aware of any of these feelings, but who knew what unconscious thoughts and emotions might be hidden there in his own brain cells? Kaliinin? Did he feel that way about her? So quickly? Or was it the abnormal tensions of this fantastic voyage into the brain that had brought about fantastic responses?

It was only then that he noticed that the screen had fuzzed out completely. He was about to shout a warning to Dezhnev to stop the motors while he concentrated and tried to recapture the waves when Dezhnev's voice boomed out.

"There it is, Albert. You guided us to the cell like a bloodhound. Congratulations!"

"Also," said Boranova, gazing at Konev's lowering countenance, "congratulations to Yuri for coming up with the idea and persuading Albert to make the effort."

Konev's face relaxed and Dezhnev said, "But now, how do we get inide?"

56.

Morrison stared at the vista ahead with interest. What he saw was a vast ridged wall stretching up and down, right and left, as far as the ship's light made it possible to see. The ridges were themselves broken up into domes so that, on closer inspection, the wall seemed to be a checkerboard with each square bulging outward. There were ragged extensions jutting outward between the bulges, like thick, short, and branching ropes that gave the wall an appearance of being tattered.

Morrison, with some effort, allowed for his own miniaturization and grasped the fact that the bulges were the ends of molecules (of phospholipids, he assumed) that made up the cell membrane. He realized with some dismay just what it meant for the ship to be the size of a glucose molecule. The cell was an enormous object; by present ship measure, it must be many kilometers across.

Konev had been staring at the cell membrane also, but emerged from his thoughtful contemplation sooner than Morrison did.

"I'm not sure," said Konev, "that this is a brain cell - or, at least, a neuron."

"What else can it be?" said Dezhnev. "We're in the brain and that's a cell."

Konev made no visible attempt to smother the disgust in his expression as he said, "There is more than one kind of brain cell. The neuron is the important cell, the chief agent of the mind. There are ten billion of them in the human brain. There are also some ten times as many glial cells of several kinds, which serve supporting and subsidiary functions. They are considerably smaller than the neurons. On the basis of chance, then, it is ten to one that this is a glia. The thought waves are in the neurons."

Boranova said, "We can't be guided simply by chance, Yuri. Can you tell in some definitive way whether this is glia or a neuron without involving statistics?"

"Not just by looking at it, no. From this size, all I see is a small section of a cell membrane and in such a case one cell looks like another. We'll have to become larger and get a more panoramic view. I presume we can become larger now, Natalya. After all, we're through what you called the collagen jungle."

"We can deminiaturize, if necessary," said Boranova, "but increasing size is more tedious and risky than decreasing it. An increase means the generation of heat and must be done slowly. Is there any alternative?"

Konev said tartly, "We might try Albert's instrument again. Albert, can you tell us if the skeptic waves you can detect are coming from straight ahead or from a slightly different direction?"

Morrison hesitated. Before his instrument had fuzzed out at a time just before the cell had been sighted, there had been the Kaliinin vision and he didn't want it back. It was too embarrassing, too upsetting. Surely, if his mind hid and suppressed emotions, it was because they were better hidden and suppressed.

He said uncertainly, "I'm not sure -"

"Try it," said Konev and all four Soviets were now looking at Morrison earnestly.

With an inward shrug, Morrison put his computer into action. After some consideration, he said, "I get the waves, Yuri, but not as strongly as I did on the way here."

"Do they get stronger in another direction?"

"Slightly, from a more upward direction, but I must warn you again that the directional abilities of my device are very primitive."

"Yes, like this ship you complain about. - Here is what it seems to me has happened, Natalya. Coming here, we were able to detect a neuron directly above the top of a glia that lay before it. When he saw the glia, Arkady naturally steered for it and its bulk now masks the neuron and we get the thought waves more dimly."

"In that case," said Boranova, "we must go over the glia to the neuron."

"And in that case," said Konev, "I say again that we must deminiaturize. At our present glucose size, the distance we must pass in moving over the glia may well prove to be a hundred or a hundred and fifty kilometers. If we increase in length ten times, say to the size and mass of a small protein molecule, we would reduce the apparent distance to merely ten or fifteen kilometers."

Kaliinin said in an abstracted voice, as though what she had to say bore no relationship to what had just been said, "We will have to be our present size to get into the neuron, Natalya."

And, after a short pause, as though disengaging himself from the possibility of directly answering the remark, Konev said, "Of course. Once we reach the neuron, we readjust our size to whatever seems best."

Boranova sighed and seemed lost in her own thought.

Konev said with unaccustomed gentleness, "Natalya, we'll have to change size eventually. We can't stay glucose size forever."

"I hate to deminiaturize oftener than I must," said Boranova.

"But we must in this case, Natalya. We cannot spend hours cruising along a cell membrane. And deminiaturizing tenfold at this stage involved a very low absolute energy change."

Morrison said, "Is it that starting the deminiaturizing process might initiate an uncontrolled and explosive continuation?"

Boranova said, "There's nothing wrong with your intuition, Albert. Without knowing anything about miniaturization theory, you manage to grasp the point. Once started, it is safest to allow the deminiaturization to continue. Stopping it involves a certain risk."

"So does remaining at glucose size for hours longer than we need," said Konev.

"True," said Boranova, nodding her head.

Dezhnev said, "Shall we put it to a vote and come to a people's democratic decision?"

At this, Boranova's head snapped up and her dark eyes seemed to flash. Her heavy jaws set firmly and she said, "No, Arkady. It is my responsibility to make the decision and I will increase the size of the ship." Then, abandoning the air of majesty, she said, "Of course you can wish me well."

Dezhnev said, "And why not? It would be the same as wishing all of ourselves well."

Boranova bent over her controls and Morrison grew quickly tired of trying to watch. He couldn't actually see what she was doing, wouldn't understand that she was doing if he did see it, and there was the mundane fact that his neck was beginning to ache with the effort to keep it turned. He looked forward and found Konev peering at him over his shoulder.

"About the skeptic wave detection," said Konev.

"What about the skeptic wave detection?" said Morrison.

"When we were making our way to this cell through the collagen jungle -"

"Yes yes, what about it?"

"Did you get any - images?"

Morrison remembered that tearing vision of Sophia Kaliinin. Nothing like it existed in his mind now. Even when he thought of it as it had then been, it now roused no response. Whatever it was in his mind, it seemed to have been reached only under the intense stimulation of concentrated skeptic waves; and whatever it was, he was not going to describe it to Konev - or to anyone else, for that matter.

He temporized, "Why should I have sensed any images?"

"Because you did on occasion when you analyzed skeptic waves at normal-size intensities."

"You're assuming that analysis during miniaturization would produce greater intensities or possess greater image-producing powers."

"It's a reasonable assumption. But did you or didn't you? The question doesn't involve theorizing. I'm asking about an observation. Did you get any images?"

And Morrison sighed inwardly and said, "No."

Konev continued his sidewise peering (under which Morrison felt himself grow a little restless and rather more than a little irate), then said softly, "I did."

"You did?" Morrison's eyes widened in honest surprise. Then, more cautiously, "What did you sense?"

"Not much, but I thought you might have gotten it more clearly. You were actually holding and manipulating your detector and it is probably more adapted to your brain than mine."

"Just what was it you got? Can you can describe it at all?"

"A kind of flicker that moved into and out of awareness. It seemed to me that I saw three human figures, one larger than the others."

"And what did you make of that?"

"Well, Shapirov had a daughter whom he adored and she had two children whom he also adored. I imagine that in his coma he may have been thinking of them, or remembering them, or being under the delusion that he was seeing them. Who knows what goes on in a coma?"

"Do you know his daughter and his grandchildren? Did you recognize them?"

"I was seeing them, as it were, through translucent glass in the twilight. It was all I could do to sense three figures." He sounded disappointed. "I had hoped you would see it more clearly."

Morrison, thinking hard, said, "I neither saw, nor sensed, anything like that."

Konev said, "Of course, things should be sharper once we are inside a neuron. It is not images we must sense, in any case. We want to hear words."

"I've never heard words," said Morrison, shaking his head.

"Of course not," said Konev, "since you worked with animals who don't use words."

"True," said Morrison. "Just the same, I once managed to run some tests on a human being, though I never reported it. I sensed no words then or images either."

Konev shrugged it off.

Morrison said, "You know, under the circumstances, it might be natural for Shapirov's mind to be full of family - if we accept your interpretation of what you thought you sensed. What would the chances be that he would be thinking of some esoteric extension of miniaturization mathematics?"

"He was a physicist. Even his family came second to that. If we can sense words out of those skeptic waves, they'll be words dealing with physics."

"You think that, do you?"

"I am positive."

The two fell quiet and for a few minutes there was no sound in the ship. Then Boranova said, "I've deminiaturized the ship to protein size and I have brought the process to a halt."

A moment passed and then Dezhnev, with an unaccustomed tightness to his throaty voice, said, "Are things all right, Natasha?"

Boranova said, "The mere fact that you can ask the question, Arkady, is an answer in the positive. Deminiaturization has stopped without incident."

She smiled, but there was a definite trace of perspiration glistening at her hairline.

57.

The surface of the glial cell still stretched out as far as the eye could see into the dimness beyond the reach of the ship's light, but it had changed in character. The domes and ridges had faded out into a fine texture. The ropes that had extended from between the domes had become threads nearly impossible to see as the ship sped along the surface.

Morrison's attention was, for the most part, on his computer, as he watched to see that the skeptic waves did not decline in intensity, but, periodically, he could not help but drift away from that and gaze at the panorama outside.

Occasionally, there would emerge from the surface of the cell the typical dendritic processes of a nerve cell - even one that was merely a subsidiary glial cell. They branched and sub-branched like a tree in winter, growing out of the cell membrane.

Even at the new and larger size of the ship, the dendrites were large when they emerged from the cell. They were like tree trunks, which, however, narrowed rapidly and were clearly flexible. Lacking the rigidity of the cartilage fibers, they swayed in the eddies set up by the ship's progress through the extracellular fluid. They swayed, indeed, at the ship's approach and Dezhnev rarely had to do anything to avoid them. They would bend out of line and the ship would pass them safely.

Collagen fibers were fewer in the immediate neighborhood of the cell and, thanks to the larger size of the ship, were much thinner and more fragile. On one occasion, Dezhnev either did not see one looming directly ahead of the ship or did not care that it was. The ship brushed past it in a way that brought it just outside Morrison's seat. He flinched at the grating collision, but the ship was in no way damaged. It was the collagen fiber that bent, then snapped and dangled free. Morrison's head turned and his eyes followed the broken fiber for the second or so that it remained in view before floating away.

Boranova must have seen it, too, and watched Morrison's reaction, for she said, "There's no reason for concern. There are trillions of those fibers scattered through the brain, so that one more or less doesn't matter. Besides, they heal - even in a brain as badly damaged as poor Shapirov's."

"I suppose so," said Morrison, "yet I can't help but think we are crashing without any right through an infinitely delicate mechanism not meant for technological invasion."

"I appreciate your feeling," said Boranova, "but hardly anything in the world seems to have been brought into being by geological and biological processes with any apparent pre-vision of human interference. Humanity does a great deal of wrong to Earth and to life, some of it wittingly. - Incidentally, I'm thirsty. Are you?"

"Definitely," said Morrison.

"You'll find a cup in the little recess under your right armrest. Pass it back."

She distributed water to all five, saying matter-of-factly, "There's no shortage of water, so if you want seconds, say so."

Dezhnev looked at his cup distastefully, while keeping one hand on the controls. He sniffed at it and said, "My father used to say: 'There is no drink like pure water, provided one realizes that it is alcohol that is the purifying agent.'"

"Yes, Arkady," said Boranova. "I am quite sure your father purified his water frequently, but here on the ship, with your hands on the controls, you will have your water unpurified."

"We must all go through privations now and then," said Dezhnev, who then downed his water and made a face.

It might have been the taste of the water that caused Kaliinin to fumble between her legs. It took a moment for Morrison to realize that it was her turn to urinate and he turned his head toward the window and waited to see if another collagen fiber might go flying.

Boranova said, "I suppose, strictly speaking, it's lunchtime, but we can do without. Still -"

"Still what?" asked Dezhnev. "A good plate of piping hot borscht with sour cream?"

Boranova said, "What I have smuggled in against regulations are bits of chocolate - high-calorie, zero-fiber."

Kaliinin, who had disposed of her small damp paper towel and was shaking her hands to dry them, said, "It will rot our teeth."

"Not immediately," said Boranova, "and you can rinse your mouth with a little water to reduce the sugar residue. Who wants one?"

Four hands went up, Kaliinin's not the last. Morrison welcomed his gladly. He was fond of chocolate in any case and sucked at it to make it last longer. The taste reminded him poignantly of his boyhood in the outskirts of Muncie.

The chocolate was gone when Konev said to Morrison in a low voice, "Have you sensed anything while we've been skimming past the glial cell?"

"No," said Morrison. (He hadn't.) "Have you?"

"I thought I did. The phrase 'green fields' crossed my mind."

Morrison could not prevent himself from saying "Hmm" and for a while remained lost in thought.

"Well?" said Konev.

Morrison shrugged. "Phrases go through one's mind all the time. You hear something out of the corner of your ear, so to speak, and sometime later it penetrates your consciousness; or some stream-of-consciousness thoughts invade your mind and one phrase surfaces; or you can have an auditory hallucination of some sort."

"It crossed my mind when I was looking at your instrument and concentrating."

"You wanted to be aware of something, I suppose, and something promptly obliged by flitting through your mind in response. You get the same effect in dreams."

"No. This was real."

"How can you tell, Yuri? - I didn't sense any such thing. Did anyone else sense it, do you suppose?"

"They wouldn't. No one else was concentrating on your machine. Perhaps no one else in the ship had a brain sufficiently like yours to sense on your wavelength, so to speak."

"You're just guessing. Besides, what does the phrase mean?"

"Green fields? Shapirov had a house out in the country. He would remember the green fields."

"He might have merely supplied the image. You would supply the words."

Konev frowned, paused a moment, then said in a clearly hostile manner, "Why are you so opposed to the possibility of getting a message?"

Morrison allowed himself to be equally hostile. "Because I've been burned by reporting such sense perceptions. I've been ridiculed long enough and I have become cautious. An image of a woman and two children doesn't tell us anything. Neither does a phrase like 'green fields.' If you report it, how can you possibly tell it from a self-generated image or phrase? Now listen, Yuri, a hint, to be useful, must, however vaguely and indirectly, tie in with the quantum-relativity relationship. That we can report. Anything less than that is not compelling; it won't force belief. It will only succeed in hurting us. I speak from experience."

Konev said, "What, then, if you succeed in hearing something vital, something that bears on our project? Will you perhaps keep it to yourself?"

"Why should I? If I sense something in physics relating to miniaturization, I would lack the background to understand it and keeping it to myself would get me nowhere. If some useful result is shared between us, this computer remains my machine and it is activated by my theory. I am the one who will get the major share of the credit. I won't keep it to myself, Yuri. Both my self-interest and my honor as a scientist will keep me from doing that. - And what about you?"

"Of course I'll share whatever I sense. I have been doing so just now."

"I don't mean 'green fields.' That is nonsense. Suppose you sense something very significant and I don't. Might it not occur to you that the knowledge would be a state secret, as miniaturization itself is? Would you then tell me that knowledge and risk the wrath of your Central Coordinating Committee."

They had been speaking in whispers, heads together, but Boranova's ears picked up the key word. "Politics, gentlemen?" she asked frostily.

Konev said, "We're discussing the possible uses of Albert's instrument, Natalya. If I learn something of importance from Shapirov's skeptic waves and Albert does not, he thinks I will keep it from him under the excuse that it is a state secret."

Boranova said, "It well may be."

Konev said mildly, "We need Albert's cooperation. It is his machine and his program and I am sure he knows how to work it at less than perfect efficiency. If he is not completely assured of our honesty and goodwill, he may arrange to have us sense nothing. I am willing to share anything that I sense if he will do the same."

"The Committee may disapprove, as Albert himself pointed out," said Boranova.

"Let it. I don't concern myself with it," said Konev.

"I'll prove I love you, Yuri," interposed Dezhnev with a chuckle. "I won't quote you."

Kaliinin said, "Natalya, I agree that we should be honest with Albert, since we must ask him to be honest with us. Using his own device with which he has experience, he is far more likely to come up with something useful than we are. A policy of quid pro quo is likely to be far more to our advantage than to his. - Isn't that so, Albert?"

Morrison nodded. "I've been thinking precisely that and would have mentioned it if it looked as though you were going to tell me that it was against government policy to be honest with me."

Boranova said, "Well, let us await events." The tension died down.

Morrison remained busy with his own thoughts, watching his machine only in abstraction.

And then Dezhnev said, "There's another cell just ahead - a kilometer or two. It looks as though it might be larger than the one we've been passing. Is that a neuron, Yuri?"

Konev, who seemed to have been in a brown study of his own, snapped to attention. "Albert, what does your machine say? Is that a neuron?"

Morrison was already handling his device. "It must be," he said. "I've never seen the skeptic waves this sharp."

"Good!" said Dezhnev. "Now what?"

58.

Kaliinin looked thoughtfully at the cell surface below. She said, "Natalya, we'll have to miniaturize to glucose size again. Arkady, get us in among the dendrites so that we can get down to the surface of the cell body."

Morrison watched the surface also. The dendrites were much more elaborate than those on the glia. The nearest one branched and branched again until it looked like a fuzzy frond vanishing beyond the reach of ship's light. Others, farther away, were fuzzier and smaller.

Morrison suspected that the fuzziness was at least partly the result of Brownian motion. Surely there couldn't be much of that, however. Probably each final strand of the branchings - each twig - met a similar twig or some neighboring neuron to form that intimate near-touch called a synapse. The wavering of the twig would not be strong enough to break the contact or the brain couldn't do its work.

Dezhnev had the ship approach the surface of the cell body, slowly slithering past the nearest dendrite (he was learning to handle the unbalance of the individual engines with a certain finesse, Morrison thought) - and, as he did so, it seemed to Morrison that the surface of the neuron was changing character.

Of course, it had to, for the ship was miniaturizing again. The ridges in the cell surface were becoming more prominent and were dividing into domes. Between the phospholipid domes the hairs were becoming ropier. Receptors, thought Morrison. Each one of them was designed to link on to a particular molecule that would be useful to the neuron and certainly glucose would he the most useful of those.

The downward change was considerably more rapid than the upward change. Absorbing energy was simple, while the energy release of deminiaturization was dangerous. Morrison understood that well by now.

Kaliinin said, frowning in concern, "I don't know which receptors are for glucose, but a great many of them must be. Skim across them slowly, Arkady - very slowly. If we're caught, I don't want to tear loose - or to tear them loose, either."

"No problem, little Sophie," said Dezhnev. "If I shut off the motors, the ship stops at once. It can't push through the giant atoms that surround us at all easily. Too viscous. So I just give it a touch of energy, enough to shoulder our way past the molecules of water, and we'll tiptoe across the receptors."

"'Through the tulips,'" said Morrison, looking at Konev.

"What?" said Konev, looking both annoyed and puzzled.

"It's a phrase that went through my head. There's an old show tune called 'Tip Toe Through the Tulips With Me,' In English, the words are -"

"What nonsense are you speaking?" snapped Konev.

"I'm trying to point out that whenever someone says 'tiptoe' to me, I automatically hear the phrase 'through the tulips' in my mind. If I happen to be concentrating on my computer when someone says 'tiptoe,' I will still hear the phrase in my mind and it will not mean that I am getting it from the skeptic waves on the computer. Do you take my meaning?"

"You're talking emptily," said Konev. "Leave me alone."

But he looked shaken, Morrison thought. He had taken the meaning.

They were now moving parallel to the surface of the neuron. The receptors were moving gently and Morrison realized that he couldn't tell which were empty and which had attached themselves to some of the molecules moving through the extracellular fluid with them.

He tried to concentrate on those molecules. There seemed to be glitterings in the fluid which might have been the light of the ship's beacon reflected from molecules, but none of it showed up well. Even the surface of the cell membrane wasn't actually clear if you looked at it directly. It was more the surrealistic impression of a surface than an actual one - too few photons were being reflected and too few were reaching them on their small scale.

Still, by the glitter, he could make out a kind of grittiness in the fluid they were passing through (water molecules, surely) and among them, now and then, something wormy-twisting, turning, closing up, then opening again. The immediate neighborhood of the ship was, of course, within the miniaturization field, so that atoms and molecules of the standard-size world were constantly shrinking as they entered - and expanding again as they left. The number of atoms doing so must be enormous but the energy change that resulted, even totaled over that number, were small enough so that it did not drain the ship perceptibly, or bring about spontaneous deminiaturization, or do any damage. - Or, at least, it seemed to do no damage.

Morrison tried not to think about it.

Boranova said, "I don't mean to question your ability, Sophia, but please check and make sure the ship has the electrical pattern of glucose."

"I assure you it does," said Kaliinin.

And as though to give notice that that was indeed so, the ship seemed to twist in mid-fluid, judging by the sudden shift in view through the walls.

Under ordinary conditions, such a twist would have thrown every person on the ship hard against the wall or the seat arm. Mass and inertia, however, were at virtually zero and there was only a faint swaying, hardly distinguishable from that which they associated with Brownian motion.

Kaliinin said, "We've attached ourselves to a glucose receptor."

"Good," said Dezhnev. "I've turned off the motor. Now what do we do?"

"Nothing," said Kaliinin. "We let the cell do its work and we wait."

The receptor did not actually make contact with the ship. This was good, for had it come any closer it would have entered the miniaturization field and its tip would have collapsed. As it was, there was a close meeting of electrical fields only, negative to positive and positive to negative. The attractions were not the full attractions but the lesser ones that resembled hydrogen bonds. It was enough to hold, but weak enough to allow the ship to pull away somewhat, as though it were connected to the receptor by rubber bands rather than by grappling hooks.

The receptor stretched the length of the ship and was irregular in outline, as though it were embracing a pattern of bulges along the plastic hull. The hull was smooth and featureless to the eye, of course, but Morrison was quite certain that there was an electric field that bulged in just the locations where the hydroxyl groups would be in the glucopyranose structure, the bulges taking on just the shapes they would in the natural molecule.

Morrison looked out again. The receptor virtually blanked out vision on the side of the ship along which it lay. If he looked beyond the receptor, however, he could see a farther stretch of the neuron's surface, seemingly without end, for it vanished beyond the reach of the ship's light.

The neuronic surface seemed to be heaving slightly and he could see greater detail. Among the regular domes of the rank and file of phospholipid molecules, he caught occasional glimpses of an irregular mass, which he guessed to be a protein molecule that ran through the thickness of the cell membrane. It was to these molecules that the receptors were attached, which did not surprise Morrison. He knew that the receptors must be peptides - chains of amino acids. They were part of the thread of a protein backbone, sticking outward, each different receptor made up of different amino acids in a specific order so designed as to possess an electric field pattern matching (in opposing attractions and physical shape) that of the molecule it was designed to pick up.

Then, even as he watched, it seemed to him that the receptors were moving toward him. He could see them now in greater numbers and could also see that those numbers were still increasing. The receptors and the protein molecules to which they were attached seemed to be swimming through the phospholipid molecules (with a film of cholesterol molecules underneath, Morrison knew), which opened before and closed behind.

"Something's happening," said Morrison as he felt the ship's own motion through the tiny drag of inertia that remained to them at their thoroughly negligible mass.

59.

Kone said, "The surface is gathering us in."

Dezhnev nodded. "It looks like its doing this." He held up his thick and callused hand, cupping it.

"Exactly," said Konev. "It will invaginate, make a deeper and deeper cup, narrowing the neck and finally closing it, and we will be inside the cell." He seemed quite calm about it.

So was Morrison. They wanted to be inside the cell and this was the way it was done.

The receptors continued coming together, alongside each one of them some molecule - some real molecule - and in among them the feigning molecule of the ship. The cell's surface, like Dezhnev's cupped hand, closed upon them entirely and drew them in.

"Now what?" said Dezhnev.

"We're in a vesicle inside the cell," said Kaliinin. "It will grow more acid and the receptor will then detach itself from us. It and all the receptors will then return to the cell membrane."

"And we?" persisted Dezhnev.

"Since we are recognized by our electric field as a glucose molecule," said Kaliinin, "the cell will try to metabolize us - break us up into smaller fragments and extract energy from us."

Even as she spoke, the peptide receptor fell away, uncoiling.

"Is that a good idea, having it metabolize us?" asked Dezhnev.

"It won't," said Morrison. "We'll be attached to an appropriate enzyme molecule which will find that we don't react as expected. We won't take on a phosphate group, so it will be helpless and will probably release us. We're not really a glucose molecule."

"But if the enzyme molecule releases us, won't another enzyme molecule of the same type attach itself to us and try again - and so on indefinitely."

"Now that you mention it," said Morrison, rubbing his chin and absently noticing the bristles grown since his morning shave, "it may be that the first molecules won't let us go, I suppose, if we won't do the expected."

"A fine situation," said Dezhnev indignantly, slipping into his local dialect of Russian, as he always seemed to do when excited, and which Morrison always had a bit of difficulty in following. "The best we can expect is that an enzyme molecule either holds us forever all by himself or holds us forever in a relay race as we pass from one enzyme to another indefinitely. - My father used to say: 'To be saved from the jaws of a wolf by a hungry bear is no great cause for gratitude.'"

"Please notice," said Kaliinin, "that no enzyme molecule has attached itself to us."

"Why is that?" asked Morrison, who had, indeed, noticed that.

"Because of a slight change in electric charge pattern. We had to mimic a glucose molecule to get into the cell, but once in, we don't have to be one anymore. In fact, we must mimic something else."

Boranova leaned forward. "Won't any molecule we mimic be liable to metabolic change, Sophia?"

"Actually, no, Natalya," said Kaliinin. "Glucose - or any other simple sugar in the body - belongs to a certain molecular configuration, so that we call it D-glucose. I've simply altered the pattern to its mirror image. We have become L-glucose and there isn't an enzyme that will touch us now, any more than any of us are likely to put a right shoe on a left foot. - Now we can move about freely."

The vesicle which had formed on their introduction to the cellular interior had broken up and Morrison gave up as hopeless any attempt to follow what was going on. Fragments around him were enveloped by much larger enzyme molecules that seemed to embrace them and then relax. Presumably, an altered victim of the enzymatic squeeze was set free to be embraced again by another enzyme.

It was all happening at once and, Morrison knew, this was only the anaerobic portion of the process (in which no molecular oxygen was used.) It would end by breaking up the glucose molecule, with its six carbon atoms, into two three-carbon fragments.

A little energy would be produced in this fashion and the fragments would be shunted to the mitochondria for the completion of the process with the use of oxygen; a process in which the universal energy-transfer molecule, adenosine triphosphate (or ATP, for short) would be invested in order to get things started and, in the end, be produced once more in quantities substantially greater than the investment.

Morrison felt the urge to drop everything and to find a way into a mitochondrion, the small energy factory of the cell. After all, the fine details of mitochondrial processes had still not been worked out - but then he pulled away almost angrily at the thought. The skeptic waves came first. He shouted that to himself, as though trying to force a realization of priorities onto an overly curious brain that was threatening to diffuse its interests.

Apparently, the same thought occurred to Konev, for he said, "We're finally inside the neuron, Albert. Let's not be tourists. What do you find in the way of skeptic waves now?"

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