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.