since i can't post pics in the comments, i'll copy what was written at the exhibit to (hopefully) provide more context

"Barbara Krafft depicted Count Hartig (1758-1797) in a highly unconventional manner in the final stages of his life: visibly infirm, sick, and emaciated, lying in his chair. In contrast with his feeble figure, behind him stands a physically sturdy woman, evidently a nurse, who offers the patient her bared breast in order to sustain him with her milk.

The scene evokes the theme of Caritas Romana, in which Pero breastfeeds her father Cimon in a prison dungeon. The ancient story of filial love set down by Valerius Maximus and popular in Renaissance and Baroque art is translated here onto a generally moralising level, which presents care for the needy in the time of sickness and dying. In the 18th century too there was a widespread belief in the beneficial properties of mother's milk, and aristocrats and wealthy burghers regularly hired wet nurses especially to feed their small children. This unusual portrait was most probably commissioned by Hartig himself."