Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
There's a whole genre of these "women-in-prison" movies that wasn't invented in the 1970s, but it seemed to peak then. This one tried to cash in on the B-movie success of another caged women classic "The Big Doll House," which released earier the same year. It even uses a few of the same actors, including Pam Greer as a vicious prison guard, and the same skimpy prison uniforms, with female guards wearing pony tails, mini skirts, and boots. It almost makes a man want to get locked up in a woman's prison. Almost.
In the snake scene, we see the four principal female prisoners in their prison cell at night. One of them sees a black snake crawl in through the barred windows. She tears a thin wooden board off her bed and uses it to pick up the snake. Then she puts the snake on a woman sleeping in bed. She was paid to kill this woman. (It occured to me later that maybe whoever paid her put the snake in the window so she could use it as a weapon.) The woman in bed wakes up, screams, and throws the snake onto the floor. Her screams wake up the other women in the cell, one of whom grabs a bucket and beats the snake to death with it. (We see a bucket actually bashing a live snake to death!) When the guards come to investigate the commotion, the fourth woman picks up the dead snake and throws it at the guards. Then the woman who tried to use the snake as a weapon hides her guilt by saying: "Those dumb snakes! They're all over this place."
I don't know what kind of snake it is - some kind of harmless snake from the Phillipines most likely, where the movie was made. But in the movie universe, all snakes are venomous, deadly, and always want to bite and kill humans.