function multifold(id)
{
    var obj = document.getElementById(id);
    var obj_c = document.getElementById(id + '_c');

    if (obj.style.display == 'block') {
        obj.style.display = 'none';
        obj_c.innerHTML = obj_c.innerHTML.replace(/閉じる/, "開く");
    }
    else {
        obj.style.display = 'block';
        obj_c.innerHTML = obj_c.innerHTML.replace(/開く/, "閉じる");
    }
}