I stepped in dog shit right before getting on a Brooklyn-bound Q train and spent the remaining twenty-six minutes considering scent as a social factor. The first thing about dog shit is the feel of the sole of your shoe sliding beneath you. The squish is muted, but immediately there is an odor. Not one that you can smell but rather one that exists as quiet disgust in the back of your throat. A quick glance backward pushes the nausea …