It may check the secretion of milk in the nursing mother, or it may change the quality of the milk so that it almost poisons the infant.  It may cause the bladder and bowels to be evacuated, or it may prevent their evacuation.

It may so change the supply of blood in the body as to leave the head without sufficient quantity and thus bring about a fainting spell; i.e. may absolutely deprive the victim of consciousness.  In lesser degree it causes the blush, a visible manifestation of emotion often very distressing.

It may completely abolish sex power in the male, or it may bring about sex manifestations which the victim would almost rather die than show.

It may completely deenergize so that neither interest, enthusiasm, or power remains.  This is a familiar effect of sorrow but occurs in lesser degree with the form of fear called worry.

The fact is that emotion is an intense bodily response to a situation which when perceived is the state of feeling.  This intense bodily response, involving the very minutest tissues of the body, may increase the available energy, may help the bodily functioning, may stimulate the “psychical” processes, but also it may deenergize to an extraordinary degree, it may interfere with every function, including thought and action.  It may surely produce acute illness, and it may, though rarely, produce death.

Moreover, it is extraordinarily contagious.  Every one knows how a hearty laugh spreads, and how quick the response to a smile.  Indeed, emotion has probably for one of its main functions the producing of an effect on some one else, and all the world uses emotion for this purpose.  Anger is used to produce fear, sorrow to evoke sympathy, fear is to bring about relenting, a smile and laughter, friendliness, except where one smiles or laughs at some one, and then its design is to bring sorrow, anger, or pain.  The leader maintains a hopeful, joyous demeanor so that his followers may also be joyous or hopeful and thus be energized to their best.  Morale is the state of emotion of a group; it is raised when joyous, energizing emotions are set working in the group and is lowered when pessimistic deenergizing emotions become dominant.  A city or a nation becomes energized with good news and success and deenergized when the battle seems lost.

The spread of emotion from person to person by sympathetic feeling or the reverse (as when we get depressed because our enemy is happy) is a social fact of incalculable importance.  The problem of the nervous housewife is a problem of society because she gives her mood over to her family or else intensely dissatisfies its members so that the home ties are greatly weakened.

This spread of emotion was happily portrayed by a motion picture I recently saw.  Old Grouchy Moneybags, wealthy beyond measure and afflicted with gout, is seated at his breakfast table.  In the next room, seen with the all-seeing eye of the movie, the butler makes love to the very willing maid.  In the kitchen the fat cook is feeding the ever hungry butcher’s boy with gingerbread and cake, and on the back steps the household cat is purring gently in contentment.  Happiness is the predominant note.