"Arkady," she said, "move forward just a little."

The feeble current in the capillaries barely stirred the ship. Dezhnev supplied a small burst of power. (Morrison felt his almost massless body move slightly backward, since there wasn't sufficient inertia to give it a real jerk.) The nearest red corpuscles between the ship and the farther wall of the capillary drifted backward.

"Stop, stop," said Kaliinin. "Enough."

"I can't stop," said Dezhnev. "I can only cut the motors and that I've done."

"It's all right," said Kaliinin. "I have it now," then added the all-but-inevitable saving afterthought of "I think." Then: "Yes, I do have it."

Morrison felt himself sway forward very slightly. Then he noted the nearby red corpuscles, together with an occasional platelet, drift forward and pass by lazily.

In addition, he became aware of a total cessation of the Brownian motion, that faint tremble he had grown so used to that he was able to ignore it - until it stopped. Now its absence was noticeable and it produced the same sensation within Morrison as the sudden cessation of a continuous low hum would have. He stirred uneasily. It was as though his heart had stopped, even though intellectually he knew it had not.

He asked, "What's happened to the Brownian motion, Sophia?"

She replied, "We're affixed to the wall of the capillary, Albert."

Morrison nodded. If the ship was one piece with the capillary wall, so to speak, the bombarding water molecules that produced the Brownian motion would lose their effect. Their impacts would work toward moving an entire section of comparatively inert wall, instead of a tiny ship the size of a blood platelet. Naturally, the trembling would cease.

"How did you manage to affix the ship, Sophia?" he asked.

"The usual electrical forces. The capillary wall is partly protein, partly phospholipid in character. There are positively and negatively charged groups here and there. I had to detect a pattern sufficiently compact, and then produce a complementary pattern on the ship; negative where the wall is positive and vice versa. The trouble is that the ship is moving with the current, so that I have to detect it a little ahead and produce the complementary pattern before we pass it. I missed three such occasions and then we hit a region where there were no suitable patterns at all, so I had to get Arkady to move us ahead a bit into a better region. - But I made it."

"If the ship had a reverse gear," said Morrison, "there would have been no problem, would there?"

"True," said Kaliinin, "and the next ship will have one. But for now, we have only what we have."

"Quite so," put in Dezhnev. "As my father used to say: 'On tomorrow's feast, we can starve today.'"

"On the other hand," said Kaliinin, "if we had a motor that could do all we would want it to do, we would have a strong impulse to use it lavishly and that might not be so good for poor Shapirov. And it would be expensive besides. As it is, we used an electric field which is more sparing of energy than a motor would be and the price is only a little more work for me - and what of that?"

Morrison was quite certain she wasn't talking for his benefit. He said, "Are you always so philosophical?"

For a moment, her eyes widened and her nostrils tightened, but only for a moment. Then she relaxed and said with a small smile, "No, who could be? But I try."

Boranova interjected, impatiently, "Enough chat, Sophia. - Arkady, you are clearly in touch with the Grotto. What's the delay?"

Arkady held up a large hand, half-twisting in his seat to present its palm toward Boranova. "Patience, my captain. They want us to stay exactly where we are for two reasons. First, I'm sending out a carrier wave in three directions. They are locating each and using them to locate us in order to see if the location they determine jibes with what Yuri says it is by dead reckoning."

"How long will that take?"

"Who can say? A few minutes, at any rate. But then my carrier waves are not very intense and the location must be precise, so they may have to repeat the measurement several times and take a mean and calculate limits of error. After all, they have to be correct, for as my father used to say: 'Almost right is no better than wrong.'"

"Yes yes, Arkady, but that depends on the nature of the problem. What is the second reason we are waiting?"

"They're going through some observations on Pyotr Shapirov. His heartbeat has become slightly irregular."

Konev looked up, his mouth failing open slightly and his thin cheeks looking gaunt under his high cheekbones. "What! Do they say it's anything we're doing?"

"No," said Dezhnev. "Do not become a tragedian. They say nothing of the sort. And what can we be doing to Shapirov that is of any importance? We are merely a red corpuscle among red corpuscles in his bloodstream, one among trillions."

"Well, then, what's wrong?"

"Do I know?" said Dezhnev, clearly irritated. "Do they tell me? Am I a physician? I just maneuver this vessel and they pay me no mind except as a pair of hands on the controls."

Kaliinin said with a touch of sadness, "Academician Shapirov clings but weakly to life in any case. It is a wonder that he has remained in stable condition so long."

Boranova nodded. "You are right, Sophia."

Konev said savagely, "But he must continue to remain so. He can't let go now. Not now. We haven't made our measurements yet."

"We will make them," said Boranova. "An irregular heartbeat is not the end of the world, even for a man in a coma."

Konev pounded the arm of his seat with a clenched fist. "I will not lose a moment. Albert, let's begin."

Morrison was startled. He said, "What can be done here in the bloodstream?"

"A neural effect may be felt immediately outside the nerve cell."

"Surely not. Why would the neurons have axons and dendrites to channel the impulse if it was going to spread and weaken into space beyond? Locomotives move along rails, telephone messages along wires, neural impulses -"

"Don't argue the case, Albert. Let's not accept failure by some fine process of reasoning. Let's test the matter. See if you can detect brain waves and if you can analyze them in the proper fashion."

Morrison said, "I'll try, but don't order me around in that bullying tone."

"I'm sorry," said Konev, not sounding sorry at all. "I want to watch what you do." He unclasped himself, turned in his seat, holding on tightly, muttering, "We must have more room the next time."

"An ocean liner, certainly," said Dezhnev. "Next time."

"What we have to do first," said Morrison, "is to discover whether we can detect anything at all. The trouble is, we are surrounded by electromagnetic fields. The muscles are rich in them and each molecule, almost, is the origin point of a -"

"Take all that as known," said Konev.

"I am only filling in the time while I carry my device through some necessary steps. The neural field is characteristic in several ways and by adjusting the computer to eliminate fields without those characteristics, I leave only what the neurons produce. We blank out all microfields like so and we deflect the muscle fields in this manner -"

"In what manner?" demanded Konev.

"I describe it in my papers."

"But I didn't see what you did."

Wordlessly, Morrison repeated the maneuver slowly.

"Oh," said Konev.

"And by now we should be detecting only neural waves if any are present here to detect - and there aren't."

Konev's right fist clenched. "Are you sure?"

"The screen shows a horizontal line. Nothing else."

"It's quivering."

"Noise. Possibly from the ship's own electric field, which is complex and not entirely like any of the natural fields of the body. I've never had to adjust a computer to filter out an artificial field."