The most suggestive bit of cinema ever might be Marlene Dietrich, dressed in a tuxedo, singing in that sweltering African cafe, pausing to kiss a woman full on the lips before tossing a flower to a stunned Gary Cooper.
But all these years later, with Jennifer Garner and Eva Longoria appearing on network television in one scanty outfit after another, does that image from "Morocco," now 75 years old, retain its elemental power?
"All I can tell you is that my students see 'Morocco' and 'It Happened One Night' all the time, and they find these films to be very moving sexually, very erotic, as did audiences at the time," says Jeanine Basinger, chairwoman of the film studies department at Wesleyan University in Middletown, Conn.
"It's about being able to put images on the screen that make you feel something. Film is about response. And sex is about response. Film can connect to an audience's sexual feelings by manipulating them through the tools of cinema."
"Morocco" and "It Happened One Night" are two films that managed this trick.
They are among 80 movies included in a new collection of essays, "The X List: The National Society of Film Critics' Guide to the Movies That Turn Us On."
The movies on the X List are, with a couple of exceptions, not pornography. Nor are they all masterpieces. Many would not even be considered good rentals, but when taken together, they at least attempt to define what does turn us on rather than what should not. And the critics' essays remind us that what we consider erotic remains intensely personal.
Consider the 1981 potboiler "Body Heat," written and directed by Lawrence Kasdan.
Roger Ebert includes it in his list of "Great Movies," and Peter Travers, who wrote the essay in "The X List," clearly agrees.
But seminal critic Pauline Kael dismissed it, citing its "insinuating, hotted-up dialogue that it would be fun to hoot at if only the hushed, sleepwalking manner of the film didn't make you cringe or yawn."
For Kael, the idea that anyone would go that nutty for Kathleen Turner's character is mystifying and the film, therefore, ridiculous.
Travers and Ebert disagree because, one assumes, they could easily see themselves tossing a chair through a window to engage in heated acts with Turner.
For them, the modern noir dialogue and stylized settings are part of an atmosphere, not something to be dissected.
Matched against Kelly Carlson's hyper-sexualized turn on TV's "Nip/Tuck," the coy flirtation between Claudette Colbert and Clark Gable in "It Happened One Night" seems remarkably tame.
It was not in its time.
When Gable removed his shirt to reveal that he was not wearing an undershirt, it was a shock to audiences in 1934 -- as much or more than anything in "Basic Instinct" was in 1992.
The famous hitchhiking scene in which Colbert scores a ride by showing off her legs has been stolen by everyone from "Dawson's Creek" to Aerosmith. So has the scene where Gable strings a bedsheet across their motel room to protect Colbert's modesty.
But it was not those scenes that caused Kevin Thomas of the Los Angeles Times to include the film on his list. He selected "It Happened One Night" because it "celebrates an era and style of intimacy that no longer exists." He says its erotic center is the way the couple listen to each other, something modern audiences might not appreciate.