Quote 10
IAGO
Zounds, sir, you're robbed. For shame, put on your
gown!
Your heart is burst. You have lost half your soul.
Even now, now, very now, an old black ram
Is tupping your white ewe. Arise, arise!
Awake the snorting citizens with the bell,
Or else the devil will make a grandsire of you.
Arise, I say! (1.1.94-101)
There's that reference to Brabantio being "robb'd" again. As we pointed out in the previous passage, Iago suggests that Desdemona's elopement is a kind of theft. What's interesting to us about this passage, however, is that Iago plays on fears of miscegenation (when interracial couples "intermix" via sex and/or marriage) when he says an "old black ram" (Othello) is "tupping" (sleeping with) Brabantio's "white ewe" (Desdemona). (By the way, a "ewe" is a lamb, so there's a suggestion that Desdemona's white skin makes her pure.) Iago's vivid and crude description of the lovemaking between a black man and a white woman is meant to scare Brabantio into thinking that Desdemona's lamb-like purity and whiteness are being contaminated and compromised by her sexual relationship with a black man. Not only that, Iago suggests that Othello is a "devil" that will make Brabantio the "grandsire" of black (like the devil) babies.
IAGO
She did deceive her father, marrying you,
[…]
OTHELLO
And so she did. (3.3.238; 241)
When Iago wants to make Othello suspect Desdemona's been unfaithful, he suggests a woman who disobeys and "deceive[s] her father is likely to screw around on her husband. Othello's response implies that he feels the same way. Instead of seeing Desdemona's decision to elope with Othello (despite her father's disapproval) as a sign of his wife's loyalty to him, Othello sees Desdemona's willingness to elope as a prelude to her infidelity. It seems that Othello's sexist assumptions leave him pretty vulnerable to Iago's plotting.
Quote 12
IAGO
Look to your wife; observe her well with Cassio;
Wear your eye thus, not jealous nor secure.
I would not have your free and noble nature,
Out of self-bounty, be abused. Look to 't.
I know our country disposition well;
In Venice they do let God see the pranks
They dare not show their husbands. Their best
conscience
Is not to leave 't undone, but keep 't unknown. (3.3.228-236)
Iago claims that Venetian women can't be trusted because they all deceive their husbands with their secret "pranks." This seems to be the dominant attitude in the play, wouldn't you say? Just about every male character in the play assumes that women are promiscuous and disloyal. Perhaps this is the reason why Iago is able to manipulate Othello into believing that Desdemona is unfaithful.
History Snack: In Elizabethan England, Venice was infamous for its courtesans (prostitutes). When Elizabethans thought about Venice, they often imagined it to be a city full of promiscuous women. Check out what Thomas Coryat has to say in his account of his travels to Venice:
[t]he name of a Courtezan of Venice is famoused over all Christendome […] The woman that professeth this trade is called in the Italian tongue Cotezana, which word is derived from the Italian word cortesia that signifieth courtesie. Because these kinds of women are said to receive courtesies of their favorites […] As for the number of these Venetian courtesans it is very great. For it is thought there are of them in the whole city and other adjacent places, as Murano, Malamocco, etc. at the least twenty thousand, whereof many are esteemed so loose that they are said to open their quivers to every arrow, a most ungodly thing without doubt that there should be tolleration of such licentious wantons in so glorious, so potent, so renowned a city." (Coryat's Crudities, 1611)