The Fastest River

The waiting room had a fish tank and three magazines from two years ago and a clock that made a sound every time the second hand moved. Soren had been counting the ticks. He was on nine hundred and forty-two.

Maya was sitting cross-legged on the floor next to the tank, watching one particular fish.

"It's been in the same corner for eleven minutes," she said.

"Fish do that," said Soren.

"I know. I'm not worried about the fish."

She wasn't, exactly. She was thinking about her dad, somewhere behind the doors that said STAFF ONLY. Routine procedure. That's what her mom had said three times. Routine. Like saying it enough would make the waiting room feel less like waiting.

Soren came and sat next to her on the floor. He had his notebook, but he hadn't opened it.

"When do you think they'll come out?" Maya asked.

"I don't know," said Soren. "How long has it been?"

"Fifty-seven minutes."

He nodded. That was honest enough.

A nurse walked past them into the break room, poured coffee, walked back out. She had not looked at them. The fish stayed in its corner.

Maya pressed her palm flat against the side of the tank. The glass was cold. Inside, the fish turned one dark eye toward her hand, then turned away.

"How much blood does a person have?" she asked. She didn't know why that was the question. It just was.

Soren thought about it. "Around five liters, I think. Give or take."

"My dad lost some. During surgery. They told my mom."

"But they give it back. Or the body makes more."

"How fast?" she asked.

He opened his notebook then. Not because he had to, but because that's where he went when something was real. He wrote the question down. How fast does blood come back?

"I don't know exactly," he said. "But I remember reading that bone marrow makes red blood cells constantly. Like, not sometimes. Always."

Maya turned away from the tank. "How many is constantly?"

Soren pulled at the edge of the page. "That's the part I don't remember."

"Let's figure it out." She stood up. "There's probably something in here."

There wasn't, unless you counted an article about preparing for a colonoscopy. But in the stairwell, held open by a rubber doorstop, there was a resident in scrubs sitting on the second step eating a granola bar, scrolling through something on her phone.

Maya looked at the woman. The woman did not look up.

"Excuse me," said Soren.

She looked up. Tired eyes. Young in a way that also looked old.

"How many red blood cells does a person make per second?"

The resident stared at him for a moment. Then she said, "Why?"

"We're figuring something out," said Maya.

The resident looked at the door to the waiting room, and seemed to understand something about who they were and why they were there. She didn't say it. She just said, "Around two million per second. Some sources say three."

Then she went back to her phone.

They went back to the fish tank. Maya sat. Soren sat beside her and wrote the number down.

Two million per second.

For a moment that was just a number. A big number, which didn't mean anything yet.

Then Soren started writing, and Maya watched him work, and her mouth opened a little because she was starting to see where it was going before he finished.

Two million per second. Sixty seconds in a minute. So a hundred and twenty million per minute. Sixty minutes in an hour. So seven billion, two hundred million per hour. Every hour. All day. While you sleep. While you sit in a waiting room counting ticks.

"In a day," said Soren, still writing, "that's over a hundred and seventy billion."

Maya was quiet.

"And there are twenty-five trillion total," he said. "Approximately."

"So in a hundred and twenty days," she said.

"Yeah." He looked up from the notebook. "The whole thing. Every single one. Replaced."

Maya pressed both hands flat on her knees and looked at the fish tank without seeing it.

"The kidneys," she said. "They're the ones who know."

"Yeah. They sense the oxygen. Like they're listening for something."

"All the time?"

"All the time. Even right now." He tapped his own chest, slightly to the left, which wasn't exactly where the kidneys were but was close enough for what he meant.

The clock ticked in the other room. Nine hundred and forty-three. Nine hundred and forty-four.

In those two seconds, Soren's body had made four million red blood cells. Maya's body had made four million more. Her dad, behind the STAFF ONLY doors, was doing the same thing. The machines were helping, and the surgeons were helping, but the bone was doing its part without being asked.

Maya had thought about her dad as still. As lying there waiting for things to happen to him. As requiring.

But his kidneys were listening right now. And somewhere in the long dark of his ribs, his bones were working.

The doors opened. Her mom came through, her face doing the complicated thing that means it's over and it was fine.

Maya stood up.

Soren closed the notebook. Then he opened it again, because there was one more thing he needed to write.

He wrote: the river never stops.

Then he stood up too, and walked with Maya toward her mother, and the fish stayed in its corner, and the clock kept its count.