About 100 students are reported to have stayed for an optional, non-credit session after the regular class on human sexuality ended.
The students were warned the after-class session would be explicit. It featured a naked woman using a sex toy to reach orgasm.
A statement from university spokesperson Alan Cubbage says, "Northwestern University faculty members engage in teaching and research on a wide variety of topics, some of them controversial and at the leading edge of their respective disciplines."
