The young ladies might behave like they were smooth and sealed as alabaster statues underneath their clothes, but then they would drop their soiled shifts on the bedchamber floor, to be whisked away and cleansed, and would thus reveal themselves to be the frail, leaking, forked bodily creatures that they really were.
-- Narrator (Volume 1, Chapter 1 paragraph 5)

Importance: This shows that while the Bennet girls held themselves are held in a higher social position than the servants, they are truly no better. In some instances they are worse because of the facade that they put on of being overly beautiful and clean, but the servants know that this is not quite the case as evidenced by their laundry. This also shows a certain laziness and arrogance about these girls as they leave their dirty and embarrassing items to be cleaned by people that are considered to be of a lower class.

But now change had come...
-- Narrator (Volume 1, Chapter 4 paragraph 94)