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“No.”

“No?”

“That’s the left atrium.”

“Right. The body. Obviously what I meant.”

“Through which vessel?”

I stare at the page. “Give me a second.”

“Mr. Fox.”

“The way you say my name is becoming increasingly hostile.”

“The vena cava.” She gives to me.

We move on. Blood enters the atrium, passes through a valve, moves into the other ventricle, travels to the lungs, returns through the left side, and leaves through the aorta.

Apparently, this complicated little circuit has kept me alive through millions of heartbeats, several questionable substances, and more bad decisions than I care to count.

I label the diagram. I label it badly. My handwriting is built for lyrics—fast, before the words leave—and on a science diagram, it looks unhinged. She corrects each label in red, with the tip of the pen.

Twenty minutes in, I’m sweating.

Actually sweating. I headlined a main stage last summer in a leather jacket, ninety-five minutes under lights that could roast a chicken, and barely glistened. Now I’m coming apart in a teaching lab in front of a five-foot-five pre-med with a red pen.

“Mr. Fox.”

“Yeah.”

“What’s confusing you about the diagram?”

I open my mouth to give her the answer I’ve offered every authority figure since childhood.

Nothing. I’m fine. I’ve got it.

But I need to learn this shit.

“Why does it need to go through the lungs halfway around? Why can’t the heart just pump it straight back out?” I gesture at the diagram. “The whole thing seems unnecessarily complicated. Bad design.”

“That’s actually a really good question,” she says.

I glance up, waiting for the sarcasm.

She picks the heart up again. Turns it in her fingers. Sets it back down between us.

“It’s oxygen,” she says. “The blood coming back from the body is used. Deoxygenated. It can’t deliver any more because it’s got nothing left to deliver. So the right side of the heart takes the used blood and sends it to the lungs to pick up more. Then the left side takes the refilled blood and sends it back out to the body. Two pumps. One loop through the lungs.”

“Right. Okay.”

“It looks inefficient because you’re picturing one pump. It’s actually two pumps working in sequence. The lungs are the refill station.”

“Refill station?”

“Yes. Two pumps, one body. One heart doing two separate jobs at the same time.”

“I take it back. Great design.” I grumble.