"'The flies trouble you, don't they, my dear?' said Mrs Bangham.
'But p'raps they'll take your mind off of it, and do you good.
What between the buryin ground, the grocer's, the waggon-stables,
and the paunch trade, the Marshalsea flies gets very large. P'raps
they're sent as a consolation, if we only know'd it. "

Paunch trade refers to the disposition of animal intestines and contents from slaughter houses.

Wonderful. Doing time with added flies. Here's a link on the Marshalsea.

http://www.britannia.com/hiddenlondon/marshalsea.html