We have a tiny dark green or black snake that suns itself near the back door on the rough brick of the house. Those bricks come from a lot of different places by the color of them, some black with generations of smoke. But the snake, it is new, shiny and sleek and has done us no harm. There is something to Emily Dickinson's "zero at the bone" even when the snake is harmless.
I can remember blackberry picking barefoot as a child and coming up on a rattlesnake. It was the noise that made me stop, and even after it moved away I was completely frozen and shivering in the July heat and unable to move for quite some time. I'm sure there are more of us who feel zero at the bone when a snake is near than those who feel nothing.
Snakes are supposed to be scary, but that doesn't mean we like the feeling. I don't think I ever read a more perfect description of it than Dickinson wrote.