What does "worrying another bone" in Chapter 9 mean in To Kill a Mockingbird?

In chapter nine of To Kill A
Mockingbird, Scout is speaking with
Atticus.

But I
was worrying another bone. Do all lawyers defend n-Negroes,
Atticus?

Scout is worried
about her father's reputation, even though she is young. When others accuse Atticus of
being a  "nigger-lover," Scout is ready to punch them with her fist. Even though she is
not quite old enough to understand, she realizes it is a negative
insult.

It is brilliant that Harper Lee uses the innocence
of an eight-year-old girl to ask questions that really shine the light on the prejudices
found in Maycomb. Scout exposes people for what they really are--prejudiced. She
understands that their prejudices are hateful and should not be allowed to exist. Scout
is offended by people's prejudices. She knows that it is wrong to be prejudiced.