On page 94 of Maus II: A Survivor's Tale, Vladek trades some of his food for a lice-free shirt that he carefully cleans and wraps in paper. He later presents the clean shirt in order to get soup.
Why did Vladek need to present a clean shirt to get soup?
He gets fed if he passes inspection. Failure to pass inspection would be punished by not getting food, or at least not good food.
Lice were important because they could bear disease and kill off the inmates more quickly. This would impede the work, because the new inmates would need to be trained. So they punish those who bear lice.
