We make them so far four principles or forms of expression, which we instance in saying that the blow of an angry man is general activity expression, shaking the fist at one, purposive expression, scowling as remnant of watching foe intently in the open air is survival expression, and twitching and trembling of certain muscles is diffusive expression. Every emotion commonly issues in all four forms, in direct activity with associated survival tendencies and purposive expression, and a surplus of energy runs over into certain natural and easy motions, or a deficiency of energy in certain organs manifests itself, the negative side of diffusive expression.[G] ----- Footnote G: Since emotion comes in waves, expression is reduplicated. This may throw some light on such an expression as laughter. Landor says the Ainu do not in the proper sense laugh, but they roar with delight. It may be that laughter is reiterated roar as resulting from reiterated psychic impulses and feelings. As in the growth of an emotion, waves are multiplied, the expression becomes more reduplicate, and thus laughter tends to become more rippling and articulate. The cachinnation and explosiveness has thus a plausible explanation, which I merely suggest. At least Prof. Dewey’s explanation (_Psychological Review_, I., 559) that “both crying and laughing fall under the same principle of action—the termination of a period of effort”—is quite too general. Tension ceasing, effort stopped, we “breathe freely,” take deep inspirations. Laughter is far from being the usual outcome of such a _status_. -----