The Knock and the Hem

My neighbour knocks the same three times on the wall when the music's too loud, and I've never once wondered what the knock means. It means it's still happening. It means stop.

There's a bacterium that, when it's under attack, copies the same short line of itself into DNA, nine letters, then nine again, then again, a strand that says nothing a dictionary would know. The best guess for now is that the pile itself is the alarm: enough of it, and a guard protein wakes up and does something drastic. So that one's a knock. The words don't matter. How many times does.

And at the ends of my own chromosomes there's a run of six letters said over and over, a thousand times or more, give or take, and every time a cell divides, a little of the end can't be copied and is lost, and what's lost is only the repeat, never the sentence. That one's a hem. It's said so often so that some of it can go.

They might be cousins, the knock and the hem. The tree puts them on one branch, an old hand in common. But the bacterium isn't saving its ends, and my cells aren't sounding an alarm. Same hand, different jobs. I don't think that's a stammer. A stammer is a word that won't come out. These come out fine. They just aren't words.

Tonight the wall is quiet, and I turn it down anyway, because I know the knock, the way I know where a hem has been let out, the soft line on the cloth where it used to end.