How do these chapters illustrate growth on Huck's part?

Huck begins to look at Jim as a fellow human being rather then a runaway slave. He hears Jim talk about his family.... how he misses them and worries about him.

In these chapter, he also begins to empathize with Mary Jane, Susan and Joanna. They aren't just girls to con or to steal from; he sees them as friends, and in the end he does the right thing by making sure the money isn't stolen.

These chapters mark Huck's first moments of maturity. Up until this point, he followed the authority of those around him, such as Pap, the Widow, Miss Watson, Judge Thatcher, and the King and Duke. The moment Huck decides to steal the money, he breaks free of this authority. For the first time, Huck acts on his convictions and morals to help other people, rather than simply acting on his personal desires.

Huck's interaction with Mary Jane also highlights an emerging aspect of his growth, namely an interest in women. In The Adventures of Tom Sawyer, Huck viewed girls as nothing more than an annoyance and did not believe they were to be taken seriously. Here, in contrast, Huck calls Mary Jane beautiful, and comments that when he saw her light a candle in the window, his "heart swelled up sudden, like to burst."

In addition, it is notable that Huck is desperate to escape the King and the Duke by the end of the Wilks ordeal. Huck is not simply scared of them (when he first meets them he compares them to his Pap), but is truly attempting to break free from the authority and control that they hold over him.

Interestingly, Jim is not a part of these scenes. However, we do meet a slave family torn apart by the King and Duke. Twain places this scene directly after Jim's emotionally charged story of his daughter's hearing loss and their subsequent separation, a very purposeful choice. Twain was vehemently opposed to slavery, and abhorred this aspect of the institution. Thus, Twain is trying to subconsciously influence his reader every step of the way by directing their emotions towards sympathy for the slaves. In observing the fate of this slave family, the reader begins to more powerfully grasp Jim's reasons for running away.