Lyric discussion by Aenema91 

Cover art for Horse Girl lyrics by These Arms Are Snakes

I'm pretty sure it's about drug use most likely heroin("find your favorite vein...push it in like a push pin") or crystal meth("deep black gums changing from the inside".) Then again "deep black gums" could be a reference to black tar heroin. That would make sense. Yeah, it's definitely about heroin.

Watch the pulse.....