It should come as no surprise to anyone that the male of the species has always had a fondness for looking upon the nude bodies of outstanding specimens of the female of the species. This erotic attachment is, of course, a central element in the propagation of the species. And while firsthand experience has always been the preferred manner of such activity, in the absence of that, various two and three-dimensional representations of such figures have had to stand in for the real thing. That is where art has come into play. But coupled with this has been a strong moralistic element that serves to restrain such tendencies except under rigidly circumscribed conditions. The figures usually had to depict Adam and Eve, who the Bible itself characterised as nude; or figures from Greek mythology, whom everyone knew cared little for anything more modest than a bit of gauze; bathers, who had good reason to be nude, or those just having finished bathing; or those disrobing and about to bathe; or allegorical figures having little or no fleshly being in the first place.
Michelangelo lived and worked within these constraints, as did artists of all nationalities for the next 300 years. By the mid 1800s however, artists, especially French artists, whom we all know to be the most sensuous of all artists, were starting to chafe a bit under such constraints. It was, in fact, incredible to see the lengths to which the great academic painters, for whom the idealised nude figure was their stock-in-trade almost, would go to depict sanitised female nudity they knew and loved in new and unique ways. Well, actually some of them weren't all that new and unique. The Paris Salon show of 1863, for example, had no less than five Birth of Venuses each strikingly different, each lusciously beautiful, each delicately idealised, but all not far removed from Sandro Botticelli's first attempt at the subject over 350 years before.
Many artists of the time seemed to have plumbed the depths of the Bible or mythology for any indication that a possible story might have include some unclothed figure, preferably female, preferably young and beautiful. Jean-Andre Rixens in 1874 decided that Cleopatra must have been nude when she invited her pet asp into her boudoir. Jean-Leon Gérôme chose the myth of Phryne in the Areopagus for his 1861 unveiling of beauty trying to persuade justice before a crowd of Greek dirty old men. Henri Gervex turned to science in his 1887 painting of a group of doctors gathered around a nude female figure as they saw demonstrated the invention of the hemostatic clamp. And if all else failed, one might do as Thomas Couture did in painting the Romans of the Decadence, simply show it all with a strongly negative moralistic title to deprecate the debauchery. Any length seemed acceptable so long as the figure was demurely nude rather than suggestively naked, as in Manet's Olympia which was rejected by that same 1863 Paris Salon with the five nude Birth of Venuses.