What is Jem's physical appearance in Chapter 1 of To Kill a Mockingbird?

Jem is about four years older than Scout, and we are told that he is “nearly ten” when the story starts.  The most specific description of Jem is of his condition at the end of the book, after the attack by Bob Ewell.

When he was nearly thirteen, my brother Jem got his arm badly broken at the elbow. …  His left arm was somewhat shorter than his right; when he stood or walked, the back...

Jem is about four years older than Scout, and we are told that he is “nearly ten” when the story starts.  The most specific description of Jem is of his condition at the end of the book, after the attack by Bob Ewell.

When he was nearly thirteen, my brother Jem got his arm badly broken at the elbow. …  His left arm was somewhat shorter than his right; when he stood or walked, the back of his hand was at right angles to his body, his thumb parallel to his thigh. (Ch. 1) 

This description would seem to indicate that the incident left a physical mark on Jem as well as an emotional one.  Jem got over it pretty quickly because he was still able to play football.   Scout begins by describing this because the incident is important to where the story ends up. 

The only description of the nearly ten-year old Jem in Chapter 1 seems to indicate that he has long or bushy hair and is taller than Dill.

Jem brushed his hair back to get a better look. “Why don’t you come over,

Charles Baker Harris?” he said. “Lord, what a name.”

“‘s not any funnier’n yours. Aunt Rachel says your name’s Jeremy Atticus Finch.”

Jem scowled. “I’m big enough to fit mine,” he said. (Ch. 1)

So Jem is tall enough to be bigger than Dill, which doesn’t appear to be too difficult since he is Scout’s age and short, and has long hair.  We learn later that it is brown.

As the book continues, we learn a little about Jem’s development.  Scout gets upset when Jem starts to eat a lot and spend less time with her.  He is starting to develop into a teenager.  He even shows Scout hair on his chest and under his arms.  To him, it means he is growing up.  To Scout, it means they are growing apart.