George is telling Lennie about their "American Dream" but while George is talking a snake crosses their path. Usually when a snake crosses your path, it means bad luck. The theme for this chapter is that if you want to accomplish your dream, your going to have obstacles in your way.
You just keep on lookin' out at the hills Lennie.
I see it George! I see the wabbits an' the farm!
Slim goes ahead and kills Curley's dog. Slim does this because the dog supposedly is holding Curley back and since the dog is old and stupid its now worthless.This is important to the story because the dog represents Lennie cause how Lennie always is holding George back.
Lennie accidentally killed Candy's Wife by braking her neck when she let him touch her hair. In the background is a puppy that Lennie also killed by petting him too hard. This is important to the story because it shows how Lennie messes up everything.
George realizes that Lennie is holding him back from his dream so after Lennie is wanted from killing someone, George puts matters into his own hands and kills Lennie. This shows how someone you have to do the wrong thing to make things better.