The Count

The waiting room had a clock with a second hand, and Maya watched it because there was nothing else to watch.

The printout was folded into a square in her fist. Her doctor had given it to her last time, when Maya asked too many questions and the doctor ran out of patience and just handed over the lab sheet so Maya could read it herself. Red blood cell count. A number with a lot of zeros. Maya had liked it so much she kept it.

The nurse at the desk was on the phone. A baby was crying somewhere down the hall. The clock ticked.

Two to three million per second.

Maya had read that on the back of the printout, in the little glossary box of fun facts that printouts always have and nobody reads. She had read it three times. She read it again now while the second hand swept from the twelve to the one.

In the time it took that hand to move one notch, her body had made two million red cells. Maybe three.

She sat very still and tried to feel it. She couldn't. That was the thing. There was no factory sound, no hum, no warmth in her arm where they did it. The most enormous thing she had ever heard of was happening inside her and it didn't even tickle.

She looked at the clock again. One second. Three million. Another second. Three million more.

Maya started doing the math the way she always did it, jumping to the end first and walking back to check. If the body had twenty-five trillion of them, and it was making millions every second, then the whole supply got swapped out eventually. Not in a day. She could tell that wasn't right. But eventually.

She pulled a pen out of her bag and wrote on the white border of the printout. Twenty-five trillion. Divided by three million a second. Her division was messy and she crossed it out twice. The number she got was somewhere around eight million seconds. She converted seconds to days the slow way, dividing by sixty and sixty and twenty-four, getting smaller each time, until she landed on a number she recognized.

About a hundred days. A little more.

Maya stopped writing.

The glossary box at the bottom of the page said it too, in print, like it had been waiting for her to arrive on her own: full replacement in approximately one hundred and twenty days.

She sat back.

In four months, none of the red cells inside her right now would still be there. Every single one would be gone, taken apart, and a new one built in its place. The blood the nurse was about to take out of her arm was not the blood she had been born with. It was not even the blood she had at her last birthday. It had all been replaced, quietly, while she did homework and slept and argued with her brother, without her ever being told.

The baby down the hall had stopped crying.

Maya looked at the clock and could not stop counting now. Three million. Three million. Three million. Each tick was a crowd bigger than every person she would ever meet, built from nothing, set loose into her, sent off to carry oxygen to her fingers so she could hold a pen.

But something didn't fit, and she chased it.

Who keeps count?

Because it had to be counted. If her body made too few, she'd go gray and tired. Too many and the blood would get thick. It landed almost exactly right, second after second, year after year, and nobody was standing inside her watching a gauge. So something was. Something had to be measuring how much oxygen was getting around and saying more or saying enough.

She flipped the printout over, looking for it. The glossary didn't say. It just listed the count and the days and stopped, the way printouts do, right before the interesting part.

Maya thought about where you would put a sensor. Not in the lungs, because the lungs only know about air coming in, not whether it reached the far places. You'd want it somewhere downstream, somewhere the blood passed through that could taste how much oxygen was left after the body had taken its share. Somewhere central. Somewhere a lot of blood went anyway.

She didn't know the answer. She wrote the question instead, in the margin, pressing hard: WHERE is the part that decides?

"Maya?" The nurse was holding the door.

Maya stood, and the printout was still in her hand, and she asked before she even got to the door, because she could not carry the question one more second.

"What part of me knows how much blood to make?"

The nurse, who was tired and had a long list of names after Maya's, blinked. "Your bone marrow makes it."

"No," Maya said, not rude, just fast. "That's the factory. I mean what tells the factory. What measures it."

The nurse paused with her hand on the door. "Huh," she said. "You know, I think it's the kidneys. They send a signal when oxygen's low. We had to learn it once." She said it like she was surprised to find it still in her head.

The kidneys.

Maya stood in the doorway and rebuilt it from that one word. The kidneys, which she had always filed under the boring drawer marked plumbing, the part everyone made jokes about. Blood ran through them constantly. They sat downstream, central, exactly where she had said a sensor should sit. They tasted the oxygen and when it ran thin they sent word, and somewhere in the dark of her bones a factory read the message and made more, three million a second, never asking her, never stopping.

The organ she'd thought was a drain was the one keeping the count.

She sat down in the chair by the table. The nurse tied the band around her arm and found the vein.

Maya watched the dark red climb into the little tube and held still, because the body that was filling it had already started replacing what was leaving, three million in the second it took to look, and would keep building her, drop by drop, sensor and factory and signal, while she sat there doing nothing at all.