This section is from the book "The Home Hand-Book of Domestic Hygiene and Rational Medicine. Volume 2.", by J. H. Kellogg, M.D.. Also available from Amazon: The Home Hand-Book of Domestic Hygiene and Rational Medicine, Volume 2.
Dislocation is usually recognized by the chin being thrown to the opposite side if the displacement occurs but on one side, and in wide gaping of the mouth when the dislocation occurs upon both sides at once. This accident is most frequently caused by yawning or violent laughing. It may be easily reduced by passing the thumbs, well protected by a bandage or towel, to the back side of the mouth and making a downward pressure upon the back teeth. When this is done the muscles of mastication draw the l»one into place. Care should be taken to avoid a recurrence of the accident, to which a person having once suffered is especially liable.