A serum that turns people into snakes

A modern Frankenstein-type (Strother Martin) experiments with snakes and human beings in the desert hills of Southern California. David (Dirk Benedict) is hired by Dr. Stoner (Martin) as a lab assistant after his previous lab assistant mysteriously went missing. As the youth falls in love with Stoner's daughter, Kristina (Heather Menzies), the doctor begins injecting David with some king of snake serum.

Released in 1973, the curiously titled "SSSssss" is a pretty decent horror flick that has the early 70s written all over it, but I can't give it... read the rest.