Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is a classic screwball comedy by the great director Preston Sturges that has a running joke throughout the movie involving the protagonist who is obsessed with snakes. The opening and closing credits even show an animated rattlesnake with a hand on its tail that holds a rattle, along with apples. You can't have a snake and a character named Eve in a movie without referring to the Garden of Eden, and a woman tempting a man into sin.
Charley Pike, "Charles" (Henry Fonda) the young son and heir of a very wealthy brewer, describes himself as an ophiologist, someone who studies snakes. He is returning home on an ocean liner after a year long expedition up the Amazon looking for snakes. He says that's how he'd like to spend all his time - in the company of men like himself in the pursuit of snakes. The other men say goodbye and tell him to beware of the dames. He tells them he's interested in "nothing but reptiles." This setup and the fact that this is a romantic comedy should alert you to the fact that Charley is going to have nothing but trouble with dames, one in particular.
In the first snake scene, a bearded man called "Professor" gives Charles a box with a snake in it. He tells him to feed it once a day - a couple of flies, a sip of milk, perhaps a pigeon's egg on Sundays, to keep her warm as he gets farther north, and to sometimes let her out of her box to play a little. (Anyone who knows anything about snakes will be laughing at this nonsense.) Professor tells Charles he named the snake after Dr. Marditz (which is a scrambled version of Ditmars, a well-known snake expert and author at the time) naming it Colobrina marzditzia, abd describing it as a rare type of Brazilian Glass Snake. Later we see Charles in the dining room of an ocean liner reading Marditz' book "Are Snakes Necessary?" They certainly are for the plot of this movie.
When Charles is in the dining room, all of the young women try to get his attention, or as Jean (Barbara Stanwyck) puts it - "Every Jane in the room is giving him the thermometer." Everybody on board knows that he is very rich and wants some of his wealth, including Jean, who is a grifter traveling with her father, a card shark. Jean tricks Charles and lures him away to fix her broken shoe. He invites her into his cabin to see "Emma" which she thinks is a new kind of ruse to get her inside. When he goes to the snake's box he discovers it has escaped. When she finds out Emma is a snake, Jean screams, then freaks out when she sees the snake crawling out of his pajamas on the bed. He tells her he was looking for snakes in the Amazon and that he's an Ophiologist. Jean asks him if he will always be interested in snakes. (Like most people, she assumes that he might grow out of what is often considered a childish interest.) He says "...snakes are my life, in a way." She says "What a life."
That night Jean gets into bed then screams in terror, still creeped out about the snake she saw in Charles' bed.
We see Charles' assistant and bodyguard Mugsy (William Demarest) a couple of times finding food for the snake.
Charles and Jean fall in love on the ship and get engaged, but when he learns that she and her father are con artists, he calls it off. Months later she is invited to the Pikes' mansion in Connecticut pretending to be the English Lady Eve Sidwich. Charles keeps more snakes in his room in the family mansion. In one scene he asks the butler if he has seen one of his snakes. The butler says he hasn't, but we see that the snake has wrapped itself around his ankle without him knowing.
Both of the snakes we see are live snakes, but they are mis-named. "Emma" is a Long-nosed Snake, Rheinocheilus lecontei, which is found in North America, not South America. And she would not know what to do with flies and milk. The second snake on the butler's ankle described as Crotalis colubrinus is a Corn Snake, from eastern North America. Although it's not a term you hear much these days, ophiology is the branch of zoology that deals with snakes, so calling himself an ophiologist is accurate.