Pump and Bellows

Bellows loved to tell the story of the day they first understood this. Pump had heard the tale a hundred times, but he never once told them to stop because he liked how the words kept time with his hands.

"When I was brand new," Bellows said, their arms rising and falling like wings, "I thought I could do everything by myself." They took a breath. "I would breathe in, then breathe out. I filled my chambers with the cleanest, sweetest oxygen you could ever imagine." They let out a small, dry laugh. "And then, absolutely nothing happened. The fresh air just sat inside my chest with nowhere to go, and not a single cell in the entire body got a drop of it."

Pump nodded in agreement, his broad shoulder muscles tensing and releasing in perfect time with the iron lever. Lub-dub.

"And I was just as foolish," Pump said. "I thought my job was the only one that mattered, believing I could save the body just by pushing blood to the very tips of the toes." He shook his head. "But it was always the same tired, dark blood traveling in circles, getting heavier with every single trip because there was no fresh air in it. Soon, the whole body started to ache from the lack of clean fuel."

Pump’s hands stayed steady on the grip, but his eyes softened because this was the part of the story he liked best.

"That was the day I found you," Pump said. "Or you found me. The glass tube was already sitting here between our desks, but we just had to learn how to use it."

"So we started the *cardiopulmonary loop*," Bellows said. "You bring me the tired blood so I can trade its old, used-up air for the fresh stuff, and then you carry the bright blood back out." They smiled. "I cannot reach the toes, and you cannot make the air."

"But together," Pump finished, his lever clicking in agreement, "the toes get their oxygen every single second of every single day."

Suddenly, a brass alarm above the desk chimed with a sharp, rising whoop-whoop that made the glass tube rattle against its metal brackets. On the wide monitor above their heads, a wireframe figure of the body scrambled up a steep, sandy hill with its legs pumping hard.

"Ah," Pump said, his posture straightening as he gripped the handle tighter, "we have a runner, and the leg muscles are already screaming for help."

"More air, more air!" Bellows called, already breathing deeper as their ribs expanded and their arms swept wide to draw in the fresh wind. "Big breaths now. In with the fresh, out with the old. Hurry, Pump!"

Pump gripped the iron lever with both hands and sped his pace, the slow lub-dub turning into a frantic gallop that shook the floorboards. "I can feel the heat in the line because the muscles are burning through their fuel and dumping a mountain of waste into the stream." He grimaced. "Bellows, this batch is incredibly heavy!"

"Then send it faster!" Bellows laughed, though they were panting heavily now, "and I will clean it as fast as you can push it!"

The dark, muddy fluid came roaring through the tube in a torrent. Every time the dark torrent hit Bellows' station, they gasped, and the fluid flashed red before shooting back to Pump in a brilliant, hot streak. The two of them moved in perfect, frantic symmetry—one heartbeat, one deep breath, over and over until they were perfectly matched.

On the screen, the runner finally reached the crest of the hill and slowed to a walk, resting hands on knees as the muscles recovered. Slowly, the glass tube cooled, the fluid slowed its frantic rush, and Pump and Bellows eased back into their quiet, steady rhythm.

"Whew," Bellows said, letting their arms drop to their sides for a brief, well-earned rest, "that was a steep hill for them to climb."

"Good work," Pump said, wiping a bead of sweat from his forehead, "because you did not miss a single drop of that heavy load."

"Neither did you," Bellows smiled.

A young apprentice from the academy had been standing in the shadow of the doorway, watching the whole sprint with wide, curious eyes. Now, he took a hesitant step into the warm room.

"I don't get it," the apprentice said, rubbing his neck as he stared at the loop, "which one of you actually gives the body its oxygen?" He looked back and forth. "Is it the heart, or is it the lungs?"

Pump and Bellows looked at each other and shared the exact same quiet smile, the kind born from years of working side by side.

"Don't look at me," Pump said, nodding toward the glass, "and don't look at Bellows, either, but watch the loop itself and what travels between us."

He gave the lever a firm push.

"See that dark fluid coming in?" Pump asked as he gave the lever another firm push, "it is full of carbon dioxide, the waste from the cells. I am the one who carries that CO2 from the body over to Bellows."

"And that is where I come in," Bellows said, opening their arms to take a slow, deep breath that filled their chest to the brim. "I let that carbon dioxide escape into the outside air when the body breathes out, then I pull in fresh oxygen and press it into the blood."

The fluid in the tube flared into a brilliant, sparkling scarlet.

"Now it is rich and ready to do some real work," Pump said, catching the bright stream and delivering it to every single cell that is waiting. He let the lever click. Lub-dub. "So, tell me. Which one of us gives the body its oxygen?"

The apprentice looked at Pump, then at the glowing tube, and finally at Bellows, chewing his lip as he thought it through.

"Neither of you," the apprentice said slowly, "or, I guess, both of you, because it is the loop itself that does the work."

"Exactly," Bellows said softly, "because you cannot have one without the other, no matter how hard either of us tries."