Isaac Asimov (21 page)

“There was no reaction. She’s not interested in me.”

“I watched her when you were lost in the alveolus. She was distraught. What was obvious to anyone then, might have been obvious to Duval much sooner—that she was attracted to you. And he might have gotten rid of you for that reason.”

Grant bit at his lower lip in thought, then said, “All right. And the loss of air. Was that an accident, too?”

Michaels shrugged. “I don’t know. I suspect you will suggest that Owens might have been responsible for that.”

“He might. He knows the ship. He designed it. He can best gimmick its controls. And only he checked on what was wrong.”

“That’s right, you know. That’s right.”

“And for that matter,” went on Grant with gathering anger, “what about the arterio-venous fistula? Was that an accident, or did you know it was there?”

Michaels sat back in his chair and looked blank. “Good Lord, I hadn’t thought of that. I give you my word, Grant, I sat here and honestly thought there wasn’t a thing that happened that could possibly point in my direction specifically. I realized that it could be maintained that I had slyly damaged the laser or undone your lifeline knot or jammed the air-chamber valve when no one was looking—or all three, for that matter. But in each case it was so much more likely that someone else had done it. The fistula, I admit, could be no one but myself.”

“That’s right.”

“Except, of course, that I didn’t know it was there. But I can’t prove that, can I?”

“No.”

Michaels said, “Do you ever read detective stories, Grant?”

“In my younger days I read quite a few. Now …”

“Your profession spoils the fun. Yes, I can well imagine that. But you know, in detective stories, it is always so simple. A subtle clue points to one person and one person only and the detective sees it though no one else does. In real life, it seems, the clues point everywhere.”

“Or nowhere,” said Grant, firmly. “We could be dealing with a series of accidents and misfortunes.”

“We could,” conceded Michaels.

Neither, however, sounded very convincing. —Or convinced.

Owens’
VOICE
sounded from the bubble, “Dr. Michaels, look ahead. Is that the turnoff?”

They could feel the
Proteus
slowing.

Michaels muttered, “Too much talk. I should have been watching.”

Immediately ahead was an open-ended tube. The thin walls facing them were ragged, fading away, almost into nothingness. The opening was barely wide enough for the
Proteus
.

“Good enough,” called out Michaels. “Head into it.”

Cora had left the workbench to look forward in wonder, but Duval remained in his place, still working, with infinite, untiring patience.

“That must be a lymphatic,” she said.

They had entered and the walls surrounded them, no thicker than those of the capillary they had left some time back.

As in the capillaries, the walls were made up, quite clearly, of cells in the shape of flat polygons, each with a rounded nucleus at the center. The fluid through which they were passing was very similar to that in the pleural cavity, sparkling yellowish in the
Proteus
headlights, and lending a yellow cast to the cells. The nuclei were deeper in color, almost orange.

Grant said, “Poached eggs! They look exactly like poached eggs!” Then, “What’s a lymphatic?”

“It’s an auxiliary circulatory system in a way,” said Cora, explaining eagerly. “Fluid squeezes out of the very thin capillaries and collects in spaces in the body and between the cells. That’s interstitial fluid. These drain off into tiny tubes or lymphatics that are open at their ends, as you saw just now. These tubes gradually combine into larger and larger tubes until the largest are the size of veins. All the lymph …”

“That’s the fluid about us?” asked Grant.

“Yes. All the lymph is collected into the largest lymphatic
of all, the thoracic duct, which leads into the subclavian vein in the upper chest and is thus restored to the main circulatory system.”

“And why have we entered the lymphatic?”

Michaels leaned back, the course momentarily secure. “Well,” he put in, “it’s a quiet backwater. There’s no pumping effect of the heart. Muscular pressures and tensions move the fluid and Benes isn’t having many of those right now. So we can be assured a quiet journey to the brain.”

“Why didn’t we enter the lymphatics to begin with, then?”

“They are small. An artery is a much better target for a hypodermic; and the arterial current was expected to carry us to target in minutes. It didn’t work out and to make our way back into an artery from here would delay us badly. Then, once we reached the artery, we would receive a battering which the ship might no longer be able to take.”

He spread out a new set of charts and called out, “Owens, are you following Chart 72-D?”

“Yes, Dr. Michaels.”

“Make sure you follow the path I’ve traced. It will take us through a minimum number of nodes.”

Grant said, “What’s that up ahead?”

Michaels looked up and froze. “Slow the ship,” he cried.

The
Proteus
decelerated vigorously. Through one portion of the wall of the now widening tube, a shapeless mass protruded, milky, granular and somehow threatening. But as they watched, it shrank and vanished.

“Move on,” said Michaels. He said to Grant, “I was afraid that white cell might be coming, but it was going, fortunately. Some of the white cells are formed in the lymph nodes, which are an important barrier against disease. They form not only white cells but also antibodies.”

“And what are antibodies?”

“Protein molecules that have the capacity to combine specifically with various outside substances invading the body; germs, toxins, foreign proteins.”

“And us?”

“And us, I suppose, under proper circumstances.”

Cora interposed. “Bacteria are trapped in the nodes, which serve as a battleground between them and the white cells. The nodes swell up and become painful. You know—Children get what are called swollen glands in the armpits or at the angle of the jaw.”

“And they’re really swollen lymph nodes.”

“That’s right.”

Grant said, “It sounds like a good idea to stay away from the lymph nodes.”

Michaels said, “We are small. Benes’ antibody system is not sensitized to us, and there is only one series of nodes we need pass through, after which we have clear sailing. It’s a chance, of course, but everything we do now is a chance. —Or,” he demanded, challengingly, “are you going to set policy by ordering me out of the lymphatic system?”

Grant shook his head, “No. Not unless someone suggests a better alternative.”

“There it is,” said Michaels, nudging Grant gently. “See it?”

“The shadow up ahead?”

“Yes. This lymphatic is one of several that enters the node, which is a spongy mass of membranes and tortuous passages. The place is full of lymphocytes …”

“What are those?”

“One of the types of white cells. They won’t bother us, I hope. Any bacteria in the circulatory system reaches a lymph node eventually. It can’t negotiate the narrow twisting channels …”

“Can we?”

“We move deliberately, Grant, and with an end in view, whereas bacteria drift blindly. You do see the difference, I hope. Once trapped in the node, the bacterium is handled by antibodies or, if that fails, by white cells mobilized for battle.”

The shadow was close now. The golden tinge of the lymph was darkening and turning cloudy. Up ahead there seemed a wall.

“Do you have the course, Owens?” Michaels called out.

“I have, but it’s going to be easy to make a wrong turning.”

“Even if you do, remember that at this moment we are heading generally upward. Keep the gravitometer indicator on the line as steadily as you can, and in the end you can’t go wrong.”

The
Proteus
made a sharp turn and suddenly all was gray. The headlights seemed to pick up nothing that was not a shadow of a deeper or lighter gray. There was an
occasional small rod, shorter than the ship and much narrower; clumps of spherical objects, quite small, and with fuzzy boundaries.

“Bacteria,” muttered Michaels. “I see them in too great detail to recognize the exact species. Isn’t that strange? Too much detail.”

The
Proteus
was moving more slowly now, following the many gentle sweeps and turns of the channel almost hesitantly.

Duval stepped to the door of the workroom. “What’s going on? I can’t work on this thing if the ship doesn’t hold a steady course. The Brownian motion is bad enough.”

“Sorry, doctor,” said Michaels, coldly. “We’re passing through a lymph node and this is the best we can do.”

Duval, looking angry, turned away.

Grant peered forward. “It’s getting messy up there, Dr. Michaels. What is that stuff that looks like seaweed or something?”

“Reticular fibers,” said Michaels.

Owens said, “Dr. Michaels.”

“Yes?”

“That fibrous stuff is getting thicker. I won’t be able to maneuver through them without doing some damage to them.”

Michaels looked thoughtful. “Don’t worry about that. Any damage we do will, in any case, be minimal.”

A clump of fibers pulled loose as the
Proteus
nudged into it, slipped and slid along the window and vanished past the sides. It happened again and again with increasing frequency.

“It’s all right, Owens,” said Michaels, encouragingly, “the body can repair damage like this without trouble.”

“I’m not worried about Benes,” called out Owens. “I’m worried about the ship. If this stuff clogs the vents, the engine will overheat. —And it’s adhering to us. Can’t you tell the difference in the engine sound?”

Grant couldn’t, and his attention turned to the outside again. The ship was nosing through a forest of tendrils now. They glinted a kind of menacing maroon in the headlights.

“We’ll get through it soon,” said Michaels, but there was a definite note of anxiety in his voice.

The way did clear a bit and now Grant could indeed
sense a difference in the sound of the engines, almost a thickening hoarseness, as though the clear echo of gases bubbling through exhaust vents were being muffled and choked off.

Owens shouted, “Dead ahead!”

There was a soggy collision of a bacterial rod with the ship. The substance of the bacterium bent about the curve of the window, sprang back into shape and bounced off, leaving a smear that washed off slowly.

There were others ahead.

“What’s going on?” said Grant in wonder.

“I think,” said Michaels, “I
think
we’re witnessing antibody reaction to bacteria. White cells aren’t involved. See! Watch the walls of the bacteria. —It’s hard by the reflection of miniaturized light, but can you see it?”

“No, I’m afraid I can’t.”

Duval’s voice sounded behind them. “I can’t see anything, either.”

Grant turned. “Is the wire adjusted, doctor?”

“Not yet,” said Duval. “I can’t work in this mess. It will have to wait. What’s this about antibodies?”

Michaels said, “As long as you’re not working, let’s have the inner lights out. Owens!”

The lights went out and the only illumination came from without, a ghostly gray-maroon flicker that placed all their faces in angry shadow.

“What’s going on outside?” asked Cora.

“That’s what I’m trying to explain,” said Michaels. “Watch the edges of the bacteria ahead.”

Grant did his best, narrowing his eyes. The light was unsteady and flickering. “You mean those small objects that look like BB-shot.”

“Exactly. They’re antibody molecules. Proteins, you know, and large enough to see on our scale. There’s one nearby. See it. See it.”

One of the small antibodies had swirled past the window. At close quarters it did not seem to be a BB-shot at all. It seemed rather larger than a BB and to be a tiny tangle of spaghetti, vaguely spherical. Thin strands, visible only as fine glints of light, protruded here and there.

“What are they doing?” asked Grant.

“Each bacterium has a distinctive cell wall made out of specific atomic groupings hooked up in a specific way. To us, the various walls look smooth and featureless; but if we
were smaller still—on the molecular scale instead of the bacterial—we’d see that each wall had a mosaic pattern, and that this mosaic was different and distinctive in each bacterial species. The antibodies can fit neatly upon this mosaic and once they cover key portions of the wall, the bacterial cell is through; it would be like blocking a man’s nose and mouth and choking him to death.

Cora said excitedly, “You can see them cluster. How—how horrible.”

“Are you sorry for the bacteria, Cora?” said Michaels, smiling.

“No, but the antibodies seem so vicious, the way they pounce.”

Michaels said, “Don’t give them human emotions. They are only molecules, moving blindly. Interatomic forces pull them against those portions of the wall which they fit and hold them there. It’s analogous to the clank of a magnet against an iron bar. Would you say the magnet attacks the iron viciously?”