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?"

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.