The subways are a disgusting, unsanitary mass transit system coated in filth, epidermal flakes, and pus—but it's not all human detritus. Anyone who's ever averted their eyes to avoid awkward late night platform conversations with chatty drunks has probably noticed accumulations of spiderweb-like subway gunk on the floor. And it turns out that gunk ISN'T psychomagnotheric slime like we've always assumed it was!

Slate's Mark Vanhoenacker went on a quest to identify the gunk, which it turns out is a form of tar called mastic, which is used to seal tunnel structures. In the summer, the mastic sometimes melts, dripping from the roof onto the platform. MTA spokeswoman Marisa Baldeo said the molten tar is "nothing to be alarmed about," and certainly we've never witnessed anyone getting slimed by it before.

New subway tunnels use different kinds of sealants, so the mastic rorschach tests that adorn certain station's floors may become a relic of the past as more and more structures are repaired. Of course, judging by the enormity of the transit system and the long-term projects currently being worked on, we don't think we'll be seeing gunk-less floors anytime soon. And even if they did disappear, we're sure it would just be replaced with some suitably gross substitute.