Isaac Asimov (16 page)

“The heart has stopped,” he cried. “Come and see.”

Cora took his place, and then Grant.

The tricuspid valve hung half open and limp. On its inner surface were the tremendous connective fibers that bound it to the inner surface of the ventricle; fibers that pulled the valve leaves back when the ventricle relaxed; and that held them firmly in position, when the contraction of the ventricle forced them together, preventing those leaves from pushing through altogether and making a reversed opening.

“The architecture is marvelous,” said Duval. “It would be magnificent to see that valve close from this angle, held by living struts designed to do their work with a combination of delicacy and strength that man himself, for all his science, cannot yet duplicate.”

“If you were to see that sight now, doctor, it would be your last,” said Michaels. “Top speed, Owens, and bear to the left, for the semilunar valve. We have thirty seconds to get out of this death trap.”

If it were a death trap, and undoubtedly it was, it was a somberly beautiful one. The walls were strutted with mighty fibers, dividing into roots that were firmly fixed to the distant walls. It was as though they saw in the distance a gigantic forest of gnarled leafless trees writhing and riven into a complex design that strengthened and held firm the most vital muscle of the human body.

That muscle, the heart, was a double pump that had to beat from well before birth to the final moment before death and do so with unbroken rhythm, unwearying strength, under all conditions. It was the greatest heart in the animal kingdom. The heart of no other mammal beat more than a billion times or so before even the most delayed approach of
death, but after a billion heartbeats the human being was merely in early middle-age, in the prime of his strength and power. Men and women had lived long enough to experience well over three billion heartbeats.

Owens’ voice broke in. “Only nineteen seconds to go, Dr. Michaels. I see no sign of the valve yet.”

“Keep on, darn it. You’re headed there. And it had better be open.”

Grant said tensely, “There it is. Isn’t that it? That dark spot?”

Michaels looked up from his chart to cast it the most cursory glance. “Yes, it is. And it’s partly open, too, enough for us. The systolic heartbeat was at the point of starting when the heart was shut down. Now, everyone, strap yourselves in tightly. We’re slamming through that opening, but the heartbeat will be right behind us and when it comes …”

“If it comes,” said Owens softly.

“When it comes,” repeated Michaels, “there’ll be a terrific surge of blood. We’ll have to stay as far ahead of it as possible.”

With determined desperation, Owens flashed the ship ahead for the tiny opening that marked the center of the crescent crack (“semilunar” for that reason) that marked the closed valve.

The operating room labored under a tense silence. The surgical team, hovering over Benes, were as motionless as he. Benes’ cold body and stopped heart brought the aura of death close above all in that room. Only the restlessly quivering sensors remained as signs of life.

In the control room, Reid said, “They’re obviously safe so far. They’re through the tricuspid and are following a curved path aiming at the semilunar valve. That’s deliberate, powered motion.

“Yes,” said Carter, watching his stopwatch in tense agony. “Twenty-four seconds left.”

“They’re almost there now.”

“Fifteen seconds left,” said Carter inexorably.

The heart technicians at the electroshock apparatus moved stealthily into position.

“Aiming straight into the semilunar valve.”

“Six seconds left. Five. Four …”

“They’re going through.” And as he spoke, a warning buzzer, ominous as death, sounded.

“Revive heartbeat,” came the word over one of the speakers, and a red button was pressed. A pacemaker went into action, and a rhythmic surge of potential made its appearance on an appropriate screen in the form of a pulsing swing of light.

The oscilloscope registering heartbeat remained dead. The pacemaker pulse was increased, while eyes watched tensely.

“It’s
got
to start,” said Carter, whose whole body tensed and pushed forward in muscular sympathy.

The
Proteus
entered the aperture, which looked like a pair of barely open lips curved in a gigantically pendulous smile. It scraped against the tough membrane above and below, hung back a moment as the engine roar raised its pitch in a temporarily vain attempt to free the ship of the sticky embrace—then lunged through.

“We’re out of the ventricle,” said Michaels, rubbing his forehead and then looking at his hand which had come away wet, “and into the pulmonary artery. —Continue at full speed, Owens. The heartbeat should start in three seconds.”

Owens looked back. He alone could do so, the others being strapped helplessly in their seat with forward vision only.

The semilunar valve was receding, still closed, with its fibers straining their points of attachments into suckers of tense tissue. With distance, the valve grew smaller, and was still closed.

Owens said, “The heartbeat isn’t coming. It isn’t … Wait, wait. There it is.” The two leaves of the valve were relaxing; the fibrous supports were falling back and their tense roots puckered and became flabby.

The aperture was gaping, the rush of blood was coming, and overtaking them was the gigantic “bar-room-m-m” of the systole.

The tidal wave of blood caught up with the
Proteus
, hurtling it forward at breakneck velocity.

The first heartbeat broke the spell in the control tower. Carter raised both hands in the air and shook them in mute invocation of the gods. “Made it, by thunder. Brought them through!”

Reid nodded. “You won that time, general. I wouldn’t have had the nerve to order them through the heart.”

The whites of Carter’s eyes were bloodshot. “I didn’t have the nerve
not
to order it. Now if they can hold up against the arterial flow …” His voice rang out into the transmitter. “Get into touch with the
Proteus
the moment their speed diminishes.”

Reid said, “They’re back in the arterial system, but they’re not heading for the brain, you know. The original injection was into the systemic circulation, into one of the main arteries leading from the left ventricle to the brain. The pulmonary artery leads from the right ventricle—to the lungs.”

“It means delay. I know that,” said Carter. “But we still have time.” He indicated the Time Recorder, which read 48.

“All right, but we’d better switch the point of maximum concentration to the respiration center.”

He made the appropriate change and the interior of the respiration post was visible on the monitor screen.

Reid said, “What’s the respiration rate?”

“Back to six per minute, colonel. I didn’t think we were going to make it there for a second.”

“Neither did we. Hold it steady. You’re going to have to worry about the ship. It will be in your sector in no time.”

“Message from the
Proteus
,” came another voice. “ALL WELL. —uh, sir? There’s more, do you want it read?”

Carter scowled. “Of course, I want it read.”

“Yes, sir. It says: WISH YOU WERE HERE AND I WERE THERE.”

Carter said, “Well, you tell Grant that I would rather a hundred times he … No, don’t tell him anything. Forget it.”

The end of the heartbeat had brought the surge forward to a manageable velocity, and the
Proteus
was moving along smoothly again, smoothly enough to make it possible to feel the soft, erratic Brownian motion.

Grant welcomed that sensation, for it could be felt only in the quiet moments and it was those quiet moments that he craved.

They were all out of their harnesses again, and Grant, at the window, found the view essentially the same as in the jugular vein. The same blue-green-violet corpuscles dominated the scene. The distant walls were more corrugated, perhaps, with the lines lying in the direction of motion.

They passed an opening.

“Not that one,” said Michaels at the console, where he labored painfully over his charts. “Can you follow my markings up there, Owens?”

“Yes, doc.”

“All right. Count the turnings as I mark them and then to the right here. Is that plain?”

Grant watched the subdivisions coming at briefer and briefer intervals, dividing off right and left, above and below, while the channel along which they cruised became narrower, the walls more plainly seen and closer at hand.

“I’d hate to get lost in this highway pattern,” said Grant, thoughtfully.

“You can’t get lost,” said Duval. “All roads lead to the lungs in this part of the body.”

Michaels’ voice was growing monotonous. “Up and right now, Owens. Straight ahead and then, uh, fourth left.”

Grant said, “No more arterio-venous fistulas, I hope, Michaels.”

Michaels shrugged him off impatiently; too absorbed to say anything.

Duval said, “Not likely. To come across two by accident is asking too much of chance. Besides we’re approaching the capillaries.”

The velocity of the bloodstream had fallen off tremendously and so had that of the
Proteus
.

Owens said, “The blood vessel is narrowing, Dr. Michaels.”

“It’s supposed to. The capillaries are the finest vessels of all; quite microscopic in size. Keep going, Owens.”

In the light of the headbeam it could be seen that the walls, as they constricted inward, had lost their furrows and creases and were becoming smooth. Their yellowness faded into cream and then into colorlessness.

They were taking on an unmistakable mosaic pattern, broken into curving polygons, each with a slightly thickened area near the center.

Cora said, “How pretty. You can see the individual cells of the capillary wall. Look, Grant.” —Then, as though remembering, “How’s your side?”

“It’s all right. Fine, in fact. You put on a very efficient band-aid, Cora. —We’re still friendly enough for the use of Cora as your name, I hope?”

“I suppose it would be rather ungrateful of me to object to that.”

“And useless, too.”

“How’s your arm?”

Grant touched it gingerly, “Hurts like the devil.”

“I’m sorry.”

“Don’t be sorry. Just—when the time comes—be very, very grateful.”

Cora’s lips tightened a bit and Grant added hurriedly, “Just my poor way of being light-hearted. How do
you
feel?”

“Quite myself. My side feels a little stiff, but not bad. And I’m not offended. —But listen, Grant.”

“When you talk, Cora, I listen.”

“Band-aids aren’t the latest medical advance, you know, and they’re not the universal panacea. Have you done anything about warding off infection?”

“I put on some iodine.”

“Well, will you see a doctor when we get out?”

“Duval?”

“You know what I mean.”

Grant said, “All right. I will.”

He turned back to the sight of the cell mosaic. The
Proteus
was creeping now, inching through the capillary. In the light of its headbeams, dim shapes could be seen through the cells.

Grant said, “The wall seems to be translucent.”

“Not surprising,” said Duval. “Those walls are less than one ten-thousandth of an inch thick. They’re quite porous, too. Life depends on material getting through those walls and through the equally thin walls that line the alveoli.”

“The which?”

For a moment, he looked at Duval in vain. The surgeon seemed more interested in what he was looking at than in Grant’s question. Cora hastened to fill the gap.

She said, “Air enters the lungs through the trachea; you know—the windpipe. That divides, just as the blood-vessels do, into smaller and smaller tubes until they finally reach the microscopic little chambers deep in the lung, where the air that enters finds itself separated from the interior of the body only by a narrow membrane; a membrane as narrow as that of the capillaries. Those chambers are the alveoli. There are about six hundred million of them in the lungs.”

“Complicated mechanism.”

“A magnificent one. Oxygen leaks across the alveolar membrane and across the capillary membrane, too. It finds itself in the bloodstream and before it can leak back, the red blood corpuscles have picked it up. Meanwhile carbon dioxide wastes leak out in the other direction from blood to lungs. Dr. Duval is waiting to watch that happen. That’s why he didn’t answer.”

“No excuses are necessary. I know what it is to be absorbed in one thing to the exclusion of another.” He grinned broadly. “I’m afraid, though, that Dr. Duval’s absorptions are not mine.”

Cora looked uncomfortable but a cry from Owens blocked off her answer.

“Straight ahead!” he called. “Watch what’s coming.”

All eyes turned ahead. A blue-green corpuscle was bumping along ahead of them, scraping its edges slowly against the walls of the capillary on either side. A wave of faint straw made its appearance at the edges and then swept inward, until all the darker color was gone.