Though Corbaccio is older and more impotent than Volpone could ever pretend to be, he hopes to hop over Volpone's grave. The carrion crow has purchased a drug for Volpone, which Mosca wisely refuses on his master's behalf. Mosca mocks the medical profession, saying that when a doctor kills a man, the law not only absolves him but gives him great rewards. Mosca relates Volpone's worsening condition by illustrating the approach of death on the face of Corbaccio. Corbaccio is pleased that Volpone is near death. Mosca cleverly obtains Corbaccio's gift of a bag of gold sequins by reminding him that Voltore left the gold plate.
Not to be satisfied with a mere bag of gold, Mosca, with cozening audacity, persuades the old, decaying Corbaccio to disinherit his brave, noble son in favor of Volpone. Corbaccio will surely outlive Volpone and the fox will gratefully, after so great a display of affection by Corbaccio, make the old crow his heir. Eventually, the son will get all of Corbaccio's inheritance and more.
Corbaccio's distracted delight, coupled with his bad hearing, enables the bold Mosca to tell him to his face that his knowledge is no better than his hearing. Volpone, playing the bedridden sick man, can hardly cover his laughter as Corbaccio exits. The two rogues re-create their triumph with gales of laughter until they are interrupted by the knock of Corvino (the raven).
Corbaccio, as the name suggests, is an old crow ready to die, living only on carrion. He is not as fearsome a bird of prey as the vulture, and Mosca is bolder in his presence. This boldness is evident in two excellent pieces of visual "business." In mimic fashion, Mosca illustrates Volpone's death throes on Corbaccio's face. Again, Mosca employs Corbaccio's hearing defect to mock his infirmity. The actor's facial expression and vocal tone belie the meaning of his rhetoric.
Hyperbole is the rhetorical device of exaggeration for effect and not to be taken as literal speech. Usually, hyperbole is used as an ornament to speech. In Jonson's case, it is an essential part of the dramatic fun. Mosca's use of hyperbole has special ironic power. He is exaggerating Volpone's condition but not Corbaccio's present state of health. Jonson's use of hyperbole as a rhetorical device in Volpone enriches the meaning of the dramatic situation. The hyperbolic intensity of the play's rhetoric increases as the plot complications become more involved.
Mosca's attempt to get Corbaccio's will made out to Volpone increases the plot complications. It is not to be supposed that the old crow's son will take his disinheritance lying down. Mosca has created another complication by cheating an innocent person.