The Museum of Modern Art has acquired a stellar and also highly personal collection of photographs from the estate of Gayle Greenhill. Among many jewels is this image of an unmade bed by Imogen Cunningham. An unmade bed is a highly erotic image which calls to mind only two things: sex and sleep. Cunningham was not the only one to evoke this sensuality. Well before Tracey Emin, Eugene Delacroix painted what in my mind is one of the most evocative paintings of an unmade bed ever. His bed also summons the agonies of sleeplessness, night terrors and the tossing and turning bequeathed to us in times of fear and want.