what does the metaphor "the common grave of mankind" suggest to the reader in "a journal of the plague year"?

So many died of the plague that eventually mass graves were used to contain all of the infected bodies. "The common grave of mankind," is a metaphor....... it shows that in death, there is no discernment between individuals. The indecency of being covered by cloth didn't matter (no one would see it); it mattered not if you were rich or poor (the final resting place was the same). The common graves held so many people they'd never have been able to keep count, and even those who'd left money enough behind to afford a coffin and real burial were denied. No one could have coffins......... there were just too many deaths.