Although Huck and Jim were different races at a time of extreme prejudice they still befriended one another.
Back in Huck's time the word nigger was very commonly used to describe African American, so this should not be used to show that Huck is not on an equal level with Jim. Huck says "Miss Watson's nigger Jim had a hair ball the size of your fist," in this quote is positively shows that Huck is just referring to Jim; he does not mean any harm by it. Also in this quotation Huck is just again referring to Jim not lowering his status "I took me fifteen minute to humble myself to a nigger." The word nigger is just use in context, most of the time, it is not meant to be demoting at this point in history. .
Another thing Huck does that only a true friend would do is he helps Jim escape, and many times passes up and opportunity for a reward for Jim. One example of this is in chapter sixteen when the two men come aboard the raft. Huck stops the men by saying that his family is on the raft with small pox; this immediately scares the men away. This is some thing only a true friend would do, especially since Jim is worth money. In the end Huck also tries to free Jim, his mutual friend, after he is recaptured. If their friend ship had not have been mutual Huck would not have felt the need to free Jim. Even though Jim was already free, Huck was unaware of this making all of his acts committed out of friend ship. .
Just by traveling down the river the two, Huck and Jim, become better friends. They make bonds that only being isolated on a raft will allow. This is shown in this quotation, " I took me fifteen minutes before I could go humble myself to a nigger," in this quote Huck is defying what he was brought up to believe and going and apologizing to Jim. This shows that there relationship has grow to the point that Huck no longer thinks of Jim as a lesser, because if Jim was a lesser Huck would not have felt the need to apologize to him.