A subtle and risque joke
This one is probably mostly invisible to modern audiences. I had to do some research before I even saw the joke, much less got it. And it's probably my favorite bit in the entire film.
Buster takes his sluggish nag to a Goat Gland Specialist -- which, I learned, was a quack that specialized in, ahem, restoring men's vim and vigor via treatments with yes, goat glands.
Buster takes his horse in to visit the goat gland specialist, and she perks up quite a bit. Then comes the priceless moment: Buster treats us to a quick, fleeting downward glance before turning and pondering the miracle worker's sign. It appears our boy Buster is assessing his manhood and contemplating a dose of goat gland for himself. Very daring for a Keaton character! He walks back inside -- but his intentions are innocent. He's only retrieving his hat.
I love that little look and could just keep rewinding and watching it again and again.