[The cause of vomiting in seasickness].

The fact that humans and some mammals vomit when suffering from any kind of motion sickness is explained on a phylogenetic basis. The swim bladder of fish develops from the same embryological origin as the stomach. In a certain group of fish the swim bladder changes its pressure and volume by contraction during sudden upward and downward movements. As the swim bladder is in very close connection with the labyrinth in many fish, it seems absolutely possible that such contraction is caused by a labyrinthine reflex influencing the N, vagus. The contraction of the muscular wall of the stomach in humans--resulting in vomiting--is, therefore, a phylogenetic heritage.