Pump and Bellows

Bellows liked to tell the story of the day they first understood it, and Pump, who had heard it a hundred times, never once told them to stop.

"When I was new," Bellows said, arms rising and falling, "I thought I could work alone. Breathe in, breathe out, all that lovely air. I filled myself up with the freshest oxygen you ever saw." They laughed a small, breathy laugh. "And then — nothing happened. The air just sat in me. It had nowhere to go. No cell in the whole body got a single bit of it."

Pump nodded along, pushing the lever. Lub-dub.

"And me," Pump said, "I thought the same. Push, push, push — I could send blood to the very tip of your smallest finger. But it was the same tired blood, round and round, getting more tired every trip. No fresh air in it. The body started to ache." Pump's rhythm stayed steady, but their voice went quiet. "That's the day I found Bellows. Or Bellows found me. The tube was already there between us. We just hadn't started using it."

"So we did," said Bellows. "You bring me the tired blood. I trade its old, used-up air for new. You carry the fresh blood out. I can't reach the toes. You can't make new air. But together—"

"Together the toes get oxygen," Pump finished. Lub-dub. "Every second of every day."

An alarm chimed — a soft, rising whoop-whoop. On the big screen above the loop, a figure was running, fast, up a long hill.

"Ah," said Pump, sitting up. "Somebody's exercising. The muscles are shouting for more."

"More air, more air!" Bellows said, already breathing deeper and faster, arms flying wider than before. "Big breaths. In through here, out with the old — hurry!"

Pump pushed the lever quicker now, the lub-dub speeding into a gallop. "I feel it — the whole loop's running hot. The muscles burned through their oxygen and dumped a mountain of leftovers into the blood. Bellows, this batch is heavy."

"Then send it faster and I'll clean it faster!" Bellows called, laughing between breaths. The dark fluid came rushing, and rushing, and each time Bellows heaved it bright again and shot it back. The two of them moved together, faster and faster, perfectly matched — one heartbeat, one breath, one heartbeat, one breath — until the runner on the screen reached the top of the hill and slowed, and the loop cooled, and they both eased back down to their steady, quiet song.

"Whew," said Bellows, arms slowing. "Good work."

"Good work back," said Pump.

A young apprentice from the academy had been watching from the doorway, and now they crept closer, staring at the loop.

"I don't get it," the apprentice admitted. "Which one of you gives the body its oxygen? Is it the heart? Or the lungs?"

Pump and Bellows looked at each other and smiled the same smile.

"Watch the loop," Pump said gently. "Don't watch me. Don't watch Bellows. Watch what goes between us." They pushed the lever. "Here comes the tired blood — see how dark? Full of the leftovers the cells breathed out. Carbon dioxide. The CO2. I'm carrying it to Bellows."

"And I open up," said Bellows, spreading wide, "and I let the CO2 go out into the air — that's you breathing out — and I pull fresh O2 in — that's you breathing in — and I press it into the blood." The fluid flared scarlet. "Now it's rich. Now it's ready."

"And I take it," said Pump, "and I carry it to every cell that's waiting." Lub-dub. "So — which one of us gives the body its oxygen?"

The apprentice looked from Pump, to the tube, to Bellows, and back to the tube. "...Neither," they said slowly. "Both. The loop does."

"There it is," said Bellows softly.