QUID PRO QUO
A quid pro quo in English describes something which is done in return for something else, a favour given with a favour received in return. In Latin it literally means something for something. In Roman times it meant the simple substitution of one thing for another, but the Romans were no strangers to mutual advantage. Rome ran on favours, and the ethic was expressed in several common phrases. Do ut des means I give so that you may give). Manus manum lavat means hand washes hand, or one hand washes the other.
Manus manum lavat is a useful sentence to remember, and not just for cynical interjections into a conversation. It has two forms of the word for hand. Manus is the nominative, the hand performing the action, and manum is the accusative, the hand receiving the action.
If you’re shaky on the different noun cases we’ve talked about, you can refresh yourself in the grammar section. Otherwise carry on to the next lesson, where we’ll be looking at a sombre but beautiful epitaph for a young girl called Mouse, or go to the general Lesson index and pick something that looks interesting.