 Clayburgh, Jill (qv)s proof of the "Snake Lemma" at the very  beginning of the movie is technically perfect. In Charles A.  Weibels book, "An Introduction to Homological Algebra" (Cambridge  U. Press, 1994), there appears the following: "We will not print the  proof (of the Snake Lemma) in these notes, because it is best done  visually. In fact, a clear proof is given by Jill Clayburgh at the  beginning of the movie Its My Turn."