How does Alan Moore use imagery in From Hell: Being a Melodrama in Sixteen Parts?

Imagery:

Hell's about right. I've seen it all 'ere lad. Alligators waddling through the shit in the gutters; albinos being led about on chains... I've stepped over kids, no more than nine, having it off in broad daylight, probably with their sisters.

All fields and gardens this was once, Godley, outside the city walls. Now look at it. Whitechapel on Friday night. Just look at it. D'ye know, there's less than two hundred and fifty lodging houses in Whitechapel? Housing eight and a half thousand people? That's, what, thirty five, forty people per house.