for(var i=0; i<$("#subject_shixun_<%= @subject.id %>").nextAll().length; i++){
    var index = parseInt($($("#subject_shixun_<%= @subject.id %>").nextAll()[i]).children(":first").html());
    $($("#subject_shixun_<%= @subject.id %>").nextAll()[i]).children(":first").html(index - 1);
}
$("#subject_shixun_<%= @subject.id %>").remove();