Read the full text of The Merchant of Venice Act 3 Scene 3 with a side-by-side translation HERE.
On a street in Venice, Shylock presses the jailer to go after Antonio, calling Antonio a fool who lent out money for free. Antonio keeps trying to plead his case, but to no avail. Shylock is hell-bent on having Antonio seized. He says they've sworn an oath, and he insists on getting the bond that was sworn for.
Shylock notes that Antonio called him a dog before he had any reason to—but now he's determined to live up to his reputation.
Continuing on his rant, Shylock demands justice from the Duke and the jailer, despite how hesitant everyone is. Shylock leaves in a huff, repeating that he'll have his bond with no interference from the Christians.
Solanio is understandably stressed out and declares Shylock to be an impenetrable dog. Antonio understands why Shylock has it in for him—often people who had forfeited their debts with Shylock moaned about it to Antonio, who then rescued them. Antonio thinks this undercutting is the reason Shylock hates him. (That and his cruel and unrelenting anti-Semitism, perhaps?)
Antonio has concluded that there's nothing the Duke can do about the situation now. Venice allows foreign nationals some commercial privileges, which keeps trade alive. If the Duke were to impose on the rights of aliens for Antonio's sake, it would compromise justice, trade, and profit in the whole diverse city.
At this point Antonio has basically given up—he's been so reduced by all this grief and loss that a pound of flesh doesn't matter to him anymore. In fact, he says, he's so wasted away that he doubts Shylock will even be able find a pound on his body to take. Resigned to his fate, he gives himself over to the jailer and hopes out loud that his beloved friend Bassanio will come see him. After that, Antonio doesn't care what happens.