jQuery动画回调问题

function thumb_wheel() {
    $(\"#slider .nivo-controlNav img\").animate({left: \'-600px\'}, 14000, function(){  
        $(this).css({left:\'0px\'}, function(){
            thumb_wheel();
        });
    });
};

this

function thumb_wheel() {
    var el = $(\"#slider .nivo-controlNav img\");
    el.animate({left: \'-600px\'}, 14000, function(){  
         el.css({left:\'0px\'});
         thumb_wheel();
    });
};