And then, after a wait of several minutes, the position came through and Konev said, "As I told you."

Morrison said, "What's the good of the position, Yuri? We don't know which way we're headed and we can only go in whatever direction that might be. Now that communications are restored, we can't steer."

Konev said, "Well, then, since there is only one way in which we can head, we will head in that direction. I'm sure that Arkady's father had a saying concerning that."

Dezhnev said at once, "He used to say: 'When only one course of action is possible, there is no difficulty in deciding what to do.'"

"You see?" said Konev. "And we will find that whatever direction we go in, we will find a way out. Move ahead, Arkady."

The ship moved forward, ploughing through the now fragile threads of collagen, splashing through a neuron, and cutting across a thin axon. (It was hard to believe they were recently inside one of those axons and that it had seemed like a highway a hundred kilometers across.)

Morrison said dryly, "Suppose that Shapirov was still alive when it became necessary for us to leave his body. What would we have done?"

"What do you mean?" said Boranova.

"I mean, what alternative is there to this? Would we not have had to determine our position? And to do that, would we not have had to establish communications? And once that was done, would we not have been able to move in only one direction - forward? Would we not have had to deminiaturize in order not to have to travel the equivalent of tens of thousands of kilometers, but merely the equivalent of a few kilometers? In short, in order to get out, would we not have had to push our way through the living neurons of a living Shapirov, as we are now pushing our way through dying and dead ones?"

Boranova said, "Well - yes."

"Where, then, is the respect for a living body? After all, we actually hesitated to violate the integrity of a dead one."

"You must understand, Albert, that this is an emergency operation with an inadequate ship. We have no choice. And, in any case, it is not like your suggestion that we deminiaturize completely in the brain, smashing the cranium and leaving Shapirov headless. Our present course, even if Shapirov was alive, would destroy a dozen neurons - or possibly a hundred - and that would not have been likely to make Shapirov's condition appreciably worse. Brain neurons are continually dying throughout life - like red corpuscles."

"Not quite," said Morrison grimly. "Red corpuscles are continually replaced. Neurons never are."

Konev interrupted, his voice rather loud, as though he were impatiently overriding the idle talk of others. "Arkady, stop. We need another position determination."

There was at once a dead silence within the ship, one that continued - as though any speech might interfere with the measurements being made in the Grotto or might hamper the concentration of those making the measurement.

Finally Dezhnev whispered the measurements to Konev, who said, "Confirm them, Arkady. Make sure you have them right."

Morrison unclasped himself. He was still virtually without mass, but there was distinctly more of it than there had been when they were maneuvering within the cell. He pulled himself cautiously upward, so that he could see the cerebrograph over Konev's shoulder.

There were two red spots on it, with a thin red line connecting them. The map displayed on the screen condensed a bit, the two dots shrinking toward each other, and then it expanded again in a different orientation.

Konev's fingers worked busily over the computer keys and the map grew double and uninterpretable. Morrison knew, however, that Konev could view it through a device that would render it stereoscopic, displaying a third dimension.

Konev laid down that device and said, "Natalya, this time chance is on our side. Wherever we are and in whatever direction we were traveling, we'd be bound to encounter a small vein sooner or later. In this case, it is sooner. We are not far away and we will strike it in such a way that we will be able to enter."

Morrison heaved an internal sigh of relief, but could not help saying, "And what would you have done if chance had dictated a vein very far away?"

Konev said coolly, "Then I would have had Dezhnev break communications again and steer to a closer one."

Dezhnev, however, turned to stare at Morrison, made a grimace of disagreement, and mouthed the words, "Not enough energy."

"Move forward, Arkady," said Boranova peremptorily, "and get to the vein."

After a few minutes, Dezhnev said, "Yuri's map is right, which I wouldn't have bet on with any enthusiasm. That's it ahead."

Morrison found himself staring at a curving wall reaching into the indefinite haze upward and downward and with just a faint suggestion of tiling to it. If it was a vein, it was as yet not very far removed from a capillary. Morrison wondered uneasily if the ship would be able to fit inside it.

Boranova said, "Is there any way, Sophia, that you can give the ship an electric charge pattern that will slip us into the vein?"

Kaliinin looked doubtful and Morrison, holding up his hand, said, "I don't think so, Natalya. The individual cells may not be entirely dead even now, but certainly the organization within them has been destroyed. I don't think any cell in the body can take us in by pinocytosis or by any other means.

"What do I do, then?" said Dezhnev unhappily, "Force my way in?"

"Of course," said Konev. "Lean against the vein wall. A small bit of it will then miniaturize and disintegrate and you can move in. You won't have to use your motors much."

"Ah," said Dezhnev, "the expert speaks. The vein will miniaturize and disintegrate at the expense of our field and that would take energy, too - more energy than forcing our way in would."

"Arkady," said Boranova, "don't be angry. This is not the time for it. Use your motors moderately and take advantage of the first weakening of the vein wall through miniaturization to burst through. Using both techniques will consume less energy than either separately."

"We can hope so," said Dezhnev, "but saying so doesn't make it so. When I was little, my father said to me once: 'Vehemence, my little son, is no guarantee of truth.' He told me this when I swore with great earnestness that I had not broken his pipe. He asked me if I understood the statement. I said I didn't and he explained it to me very carefully. Then he walloped me."

"Yes, Arkady," said Boranova, "but move in now."

Konev said, "It's not as though you're going to flood the brain with blood. It wouldn't matter now that Shapirov is dead, but, as it happens, the blood isn't flowing now. Virtually nothing will leak."

"Ah," said Dezhnev, "this raises an interesting point. Ordinarily, once we enter a vein, the blood flow would carry us in a particular direction. Without blood flow, I must use my engines - but in which direction must we go?"

"Once we penetrate at this point," said Konev calmly, "you will turn to the right. So my cerebrograph says."

"But if there is no current to turn me to the right and if I enter at an angle to the left?"

"Arkady, you will enter at an angle to the right. My cerebrograph tells me that, too. Just push in, will you?"

"Go ahead, Arkady," said Boranova. "We have no choice but to rely on Yuri's cerebrograph."

The ship moved forward and, as the prow touched the vein wall, Morrison could feel the slight vibration of the laboring motors. And then the wall simply gave and pulled away in all directions and the ship was inside.

Dezhnev stopped the motors at once. The ship moved in at a rapidly slowing pace, rebounded off the far wall (maintaining contact so briefly as to cause no damage that Morrison could see), and straightened out with the long axis of the ship along the enormous tunnel of the vein. The ship's width was better than half the width of the blood vessel.