My college level essay is on Titus Andronicus 2.4.11-57.
"Who is this - my niece that fies away so fast..."
How does the passage say what it says and how does it contribute, by means of its language and its ideas, to the work as a whole?
Demetrius and Chiron have just raped and mutilated Lavinia, cutting off her tongue and hands so that she can neither speak nor write of their crime (nor tell anyone that it wasn't her brothers who committed it, since Demetrius and Chiron plan to frame Martius and Quintus). They have also killed her husband, Bassianus.
Lavinia's uncle Marcus arrives to find his niece in her terrible condition. There's a lot you might say about his speech, but here are a couple of ideas.
Marcus's reaction helps us realize what exactly has happened to Lavinia. Since we didn't witness her rape and mutilation, and didn't fully understand Demetrius and Chiron's wicked parting puns, it's up to Marcus to bring home the horror of the situation. He wishes he were dreaming—or dead ("If I do dream, would all my wealth would wake me! / If I do wake, some planet strike me down, / That I may slumber in eternal sleep!"). He urges Lavinia to speak, but realizes (and so helps us realize) that she can't; she has lost her tongue. His exposition also helps us realize that she has been raped: "But, sure, some Tereus hath deflowered thee, / And, lest thou shouldst detect him, cut thy tongue."
Marcus also acts as a voice for the now voiceless Lavinia, explaining her feelings to us. We feel her shame as she blushes despite massive blood loss ("Ah, now thou turn'st away thy face for shame! / And, notwithstanding all this loss of blood, / As from a conduit with three issuing spouts, / Yet do thy cheeks look red as Titan's face / Blushing to be encountered with a cloud."). He emphasizes that all recourse has been taken from her: she cannot write or even sew her rapist's name like Philomela from the Greek myth. Marcus helps us feel her internal pain as clearly as her physical pain: "Sorrow concealed, like an oven stopp'd, / Doth burn the heart to cinders where it is."
Marcus also relies heavily on Classical allusions—a fad in Shakespeare's day, and also a reflection of the classical themes (and setting) of Titus Andronicus. It prepares us for events as dramatic as those of mythology—crazy stuff.