He represents Candy. The dog was old and useless as Candy will soon become.
Candy's dog also represents a symbol for what happened to Lennie. Candy stated, "I ought to have shot that dog myself, Goerge. I shouldn't ought to of let no stranger shoot my dog." George uses this quote as advice about what to do with Lennie after he killed Curley's Wife. George stole Carlsons Luger so that he could be the one to shoot Lennie. As Candy said, George didn't want a stranger to get rid of his best friend. He knew he had to do it himself.
the mice represent Lennie's personality
Candy
because they killed his dog
In "Of Mice and Men," Candy receives $250 as compensation for losing his hand in an accident on the ranch.
Candy tells George that he should have killed his dog on page 44 of Of Mice and Men.
because they killed his dog
They are both old
Hope for Lennie and George.
because they killed his dog
Candy asked for some painkiller to help with his stomach ache in "Of Mice and Men."
The swamper, Candy, is missing one of his arms.
Candy tells the story of losing his hand on page 61 of "Of Mice and Men" by John Steinbeck.