Show laughter a series of barks laughing is barking say any the scientists entis ts the neck and head are thrown back while a series of short barks aro are emitted from the throat at however musical tho the barks may be hey aro are barks tho the laugh begins with a sudden and violent contraction of ilie he muscles s of tho the chest and abdomen nut instead of opening to let the air pass out of tho the lungs lunga the vocal cords approach each other and hold it back but they are not strong enough to exercise such opposition for more than an instant and tho the air which to la under pressure promptly escapes As it does doea so it makes the vocal cords vibrate producing the bark this obstruction and liberation ot of tho the air expelled from tho the lungs repe repents fits itself again and again at intervals of a quarter of a second there are thus in a hearty laugh four barks a second d and if continued they go on at that rate as aa long ns as the air reserve in the lungs holds out the empty lungs must then themselves and this interval Is marked by a quick gasp for breath after which tho the barks are renewed tho the barks occur in series with gasps gaspa for breith breath at intervals when laughter Is violent the entire body participates the upper part of the trunk bends and straightens itsell alternately or sways to right and left the feet stamp on the floor door while the lands hands are arc pressed upon the loins to moderate tie he painful spasm |