I agree with others in that Ferdinand here makes humoural references that we’ve grown used to throughout this course, especially in Coriolanus. Here, we can see that The Cardinal is clearly phlegmatic, similarly to Menenius—he criticizes Ferdinand for his irascibility, telling him that even though he is also furious, "[he] can be angry/ Without this rupture...urging the Duke put [him]self/In tune (Act II.v.). Contrastingly, Ferdinand (obviously a choleric) whose irascibility drives him nearly insane, claiming he will “purge” her “infected blood.” It is interesting to observe how the characters' humoural urges transform one and other. There's an overall sense of wanting to preserve The Duchess as she is, for she is the sanguine positioned at the center of attention. Her excess of passion for Antonio (or independence) causes imbalance in her brothers,’ eventually allowing Bosola, the melonchloic to manipulate the situatation fueling Ferdinand’s choler and unleashing destructive forces which will mark this play’s tragic ending.
