Now, then, when you see, hear or feel anything that makes you laugh, the sensory nerves have only to receive the impression to bring on the explosion of laughter. Something touched the laugh nerves or the laugh trigger that caused it to go off. You can prove that it is a matter of impression entirely by noting that some people can listen to a perfectly funny story, even when told by a clever performer, and never crack a smile, while others burst into uncontrollable laughter, and he who does not even smile may be listening even more intently than the other--he may even be looking for a laugh. It all depends upon the impression that is made upon the nerves. The muscles have the power to express the state of gladness which is indicated by laughter when certain impressions pass along the nerves which operate them, just as they can be made to do other things when the proper cause for action is shown them. Why Do We Cry When Hurt? We cry when we are hurt for the same reason that we laugh when we are glad. The muscles and nerves, under the direction of the brain, produce the cry just as the muscles and nerves produce laughter, although they are probably, but not necessarily, a different set of muscles and nerves. When we are hurt in any part of our body or feelings the impression does not affect us until it reaches the brain. Then instantly, of course, the body and brain go to work to destroy the pain. The first thing, of course, is to give a warning to other parts of the body that there is a hurt, and our crying is a warning to other people that we are hurt. That is probably the only good that crying does. It does not remove the hurt--it only tells others of our troubles. We cry with the lower part of the brain--the only portion of the brain which is active in a little baby. This is why even a tiny baby can cry. Crying is the only thing a baby can do to give warning of its distress or discomfort. Later in life the upper part of the brain develops. This is the master of the lower part. Therefore, we do not always cry when hurt as we grow older, because the master brain sometimes tells the lower brain that to cry will not help matters in the least, even though we are inclined to cry. Sometimes the hurt or shock to older people is so great or sudden that we cry out before the controlling part of the brain has had time to get in its work of preventing the outcry, but we are able to stop crying when the master brain again secures control. Where Do Tears Come From?