function daumenKino() {
  var $alt = $('#bilderstapel IMG.obersteebene');

  if($alt.next().length)
    var $neu = $alt.next();
  else
    var $neu = $('#bilderstapel IMG:first');

  $alt.addClass('mittlereebene');
  $alt.removeClass('obersteebene');
  $neu.css({opacity: 0.0});
  $neu.addClass('obersteebene');

  $neu.animate({opacity: 1.0}, 3000, function() {
    $alt.removeClass('mittlereebene');
  });
}


$(document).ready(function() {
   setInterval( "daumenKino()", 5000 );
});