Quote 10
I could see no reason why I should, at the end of each week, pour the reward of my toil into the purse of my master. When I carried to him my weekly wages, he would, after counting the money, look me in the face with a robber-like fierceness, and ask, "Is this all?" He was satisfied with nothing less than the last cent. He would, however, when I made him six dollars, sometimes give me six cents, to encourage me. It had the opposite effect. I regarded it as a sort of admission of my right to the whole. The fact that he gave me any part of my wages was proof, to my mind, that he believed me entitled to the whole of them. (11.3)
When his master takes away the wages Douglass earns, he sometimes gives him a small part of it back. But Douglass is far from grateful; in fact, this makes him even more sure that he deserves to have all of it back. Douglass also wants to show us the impossibility of being a good slave owner: small favors only make the larger injustices sting even more.
Quote 11
I was somewhat unmanageable when I first went there, but a few months of this discipline tamed me. Mr. Covey succeeded in breaking me. I was broken in body, soul, and spirit. My natural elasticity was crushed, my intellect languished, the disposition to read departed, the cheerful spark that lingered about my eye died; the dark night of slavery closed in upon me; and behold a man transformed into a brute! (10.5)
By using words like "tamed," Douglass shows us that being "broken" doesn't simply involve physical violence: Covey transforms Douglass from a human into an animal by breaking his spirit. All of the defining characteristics of a human being get pounded out of Douglass by force until he starts to act as mindlessly and thoughtlessly as a beast in the fields.
Quote 12
After apologizing for his ignorance, and reminding the audience that slavery was a poor school for the human intellect and heart, he proceeded to narrate some of the facts in his own history as a slave, and in the course of his speech gave utterance to many noble thoughts and thrilling reflections. (Preface.4)
Partly, Douglass is just being humble. He's giving a speech in front of a big audience, and he's never had much practice or training for that kind of thing. So he wants to remind his listeners not to judge him too harshly. At the same time, though, when Douglass calls slavery a "poor school for the human intellect and heart," he's reminding people that while slaves might often not seem to be as smart or as well-spoken as white people, this isn't their fault. Instead, it's the fault of the masters who enslaved them. After all, while Southerners would often claim that black people should be slaves because they were born inferior, Douglass thinks this is backwards: slaves aren't born inferior, but rather it's slavery that makes them inferior.