Jean-Baptiste Greuze, Severus and Caracalla. 1769, Oil on canvas. Musée du Louvre.
Severus raised Caracalla's rank above his brother's, so that he would be next in line for Emperor. When the three went on a campaign in Britain the emperor fell ill. Caracalla picked up the slack for his father. It is said that he would just as well have seen his father dead so that he could be emperor. ..makes sense so far! Rumor has it that Caracalla actually tried to murder his father while on campaign. If he were so bold to attempt it, he did it unsuccessfully.
Greuze chose to depict a moment when the ill emperor calls out his son. Wrapped in cloth and mimicing Michelangelo's God (sistene chapel), the man is able to gather strength to sit up and physically and verbally direct his claim against Caracalla. Clearly the boy has not kept his feelings private. It is an intense moment between father and son, and Caracalla, who should be stunned turns around with a look more of annoyance than anything.