Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This movie is based on two of Steinbeck's short novels "Cannery Row" and its sequel, "Sweet Thursday." While Cannery Row is concerned largely with Doc and his neighbors Mac and the bums, Sweet Thursday introduces Suzy and her romantic relationship with Doc.
Doc, played by Nick Nolte, is a biologist who lives on Cannery Row in Monterey back during the 1930s depression era. Suzy, played by Debra Winger, is a vagabond who recently came to town so desperate for work that she took a job at the local brothel. They are immediately attracted to each other but keep fighting each other off. When Suzy first visits Doc, she puts a bowl of cookies on a rattlesnake cage and is startled by the rattling response. She asks why he has them and he says that he sells the venom. She says she wouldn't want to live with a bunch of filthy snakes, which offends Doc, who tells her snakes are cleaner than humans, they even shed their skin. Much later in the movie, after a few more failed attempts at romance, Doc is putting on a tie and decent clothing to visit her after she has left the brothel. He wonders if he is doing the right thing, dressing up and bringing chocolates, and he asks the rattlesnakes for their opinions. He has to bang on the glass to get them to rattle a response.
We see a live Southwestern Speckled Rattlesnake in a cage and some other live rattlesnakes, but the snakes Doc talks to are stuffed dead snakes, or fakes, and when he bangs on the glass and we hear them rattle, their rattles do not move.