Unable to hide class on click

Unable to hide class on click

Hi,

I am using the following to show and hide menu items on click, it shows the menu items when I click on the target however when I click a second time it does not hide the menu items again.

    $(document).ready(function(){
        $(".menu_sub_par_head").click(function(){
            if ($('.menu_sub_head').is(":visible")) {
             $(".menu_sub_head").hide();
            }
            else {
            $(".menu_sub_head").show();
            }
        });
    });

Any assistance would be appreciated. 

Michael.