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There is an old saying in English:Laughter is the best medicine.Until recently,few people took the saying very seriously.Now however doctors have begun to investigate laughter and the effects it has on the human body.They have found evidence that laughter really can improve peoples health. Tests were carried out to study the effects of laughter on the body.People watched funny films while doctors checked their heart rate blood pressure,breathing and muscles.It was found that laughter has similar effects to physical exercise.It increases blood pressure the heart rate and the rate of breathing; it also works several groups of muscles in the face the stomach and even the feet.If laughter exercises the body it must be beneficial. Other tests have shown that laughter appears to be capable of reducing the effect of pain on the body.In one experiment doctors produced pain in groups of students who listened to different radio programs.The group which tolerated the pain for the longest time was the group which listened to a funny program.The reason why laughter can reduce pain seems to be that it helps to produce endorphins(内啡肽)in the brain.These are natural chemicals which diminish both stress and pain. There is also some evidence to suggest that laughter helps the bodys immune system that is the system which fights infection.In an experiment,one group of students watched a funny video while another group served as the control group - in other words a group with which to compare the first group.Doctors checked the blood of the students in both groups and found that the people in the group that watched the video had an increase in the activity of their white blood cells that is the cells which fight infection. | 
