Answer: in chapter 9, boxer overworks himself and collapses, then napoleon "sends" him to the "hospital" and he dies by being sold to the "glue factory" aka the horse slaughterer, and napoleon buys alcohol with the money.
Explanation: I think the main idea is showing people the consequences of totalitarian rule when the people submit. Boxer's death marked the beginning of the animal farm's down fall. By the end they can't tell the pigs and people apart.
