How does Bill Brittain use imagery in The Wish Giver: Three Tales of Coven Tree?

Imagery:

"For the first time she could remember, Polly was deep down scared. Twice yesterday, the only sound she had been able to make was a bullfrog's deep jug-a-rum. Even now she was afraid to open her mouth for fear that the frog sound would come out. What made it happen? It wasn't any disease she'd ever heard of. And she didn't think she was going crazy."

"Sometimes she'd get so worried about Henry's plight that she'd go all sick inside and want to scream and scream, or else run off somewhere and hide. Then Sam would give her a wink or a nod or a few whispered words, and she'd find the strength to go on."