During digestion，the movements of the stomach are similar to churning.Every time you take a full breath，or when you cachinnate well，the diaphragm descends and gives the stomach an extra squeeze and shakes it.
Frequent laughing sets the stomach to dancing，hurrying up the digestive process.The heart beats faster，and sends the blood bounding through the body.“There is not，”says Dr.Green，“one remotest corner or little inlet of the minute blood-vessels of the human body that does not feel some wavelet from the convulsions occasioned by a good hearty laugh.”In medical terms，it stimulates the vasomotor centers，and the spasmodic contraction of the blood-vessels causes the blood to flow quickly.Laughter accelerates the respiration，and gives warmth and glow to the whole system.It brightens the eye，increases the perspiration，expands the chest，forces the poisoned air from the least-used lung cells，and tends to restore that exquisite poise or balance which we call health，which results from the harmonious action of all the functions of the body.This delicate poise，which may be destroyed by a sleepless night，a piece of bad news，by grief or anxiety，is often wholly restored by a good hearty laugh.
Grief，anxiety，and fear are great enemies of human life.A depressed，sour，melancholy soul，a life which has ceased to believe in its own sacredness，its own power，its own mission，a life which sinks into querulous egotism or vegetating aimlessness，has become crippled and useless.We should fight against everyinfluence which tends to depress the mind，as we would against a temptation to crime.It is undoubtedly true that，as a rule，the mind has power to lengthen the period of youthful and mature strength and beauty，preserving and renewing physical life by a stalwart mental health.
I read the other day of a man in a neighboring city who was given up to die;his relatives were sent for，and they watched at his bedside.But an old acquaintance，who called to see him，assured him smilingly that he was all right and would soon be well.He talked in such a strain that the sick man was forced to laugh;and the effort so roused his system that he rallied，and he was soon well again.