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.
Was it not Shakespeare who said that“a light heart lives long?”
Physiology tells the story.The great sympathetic nerves are closely allied;and when one set carries bad news to the head，the nerves reaching the stomach are affected，indigestion comes on，and one’s countenance becomes doleful.Laugh when you can;it is a cheap medicine.Merriment is a philosophy not well understood.The eminent surgeon Chavasse says that we ought to begin with the babies and train children to habits of mirth：“Encourage your child to be merry and laugh aloud;a good hearty laugh expands the chest and makes the blood bound merrily along.commend me to a good laugh—not to a little snickering laugh，but to one that will sound fightthrough the house.It will not only do your child good，but will be a benefit to all who hear，and be an important means of driving the blues away from a dwelling.Merriment is very catching，and spreads in a remarkable manner，few being able to resist its contagion.A hearty laugh is delightful harmony;indeed，it is the best of all music.”
“Children without hilarity，”says an eminent author，“will never amount to much.Trees without blossoms will never bear fruit.”