The benefits of humor, though, aren't all mental. Humor triggers laughter. According to physiological studies, the laughter, in turn, stimulates our cardiovascular systems by increasing the rate at which the heart beats and contracting the muscles. In fact, one study suggested that laughing one hundred times per day is the equivalent of spending ten minutes on a rowing machine. One study went so far as to suggest that the benefits of laughter reach far beyond our body system. "Laughter reduces levels of certain stress hormones which suppress the immune system, increase the number of blood platelets - which can cause obstructions in arteries, and raise blood pressure," said one researcher. "When we're laughing, natural killer cells that destroy cancer cells increase, as does the level of Gamma-interferon - a disease-fighting protein, T-cells - a major part of the immune system, and B-cells - which make disease-destroying antibodies. Laughter may also increase the concentration of salivary immunoglobulin A, which defends against infectious organisms entering through the respiratory tract so it helps us to resist colds and viruses." That makes quite a case of the adage "A barrel of laughs a day keeps the doctor away." The healing power of humor is wide-ranging in scope and situation. Though medically, the interesting healing powers of humor are still being studied by many scientists , humor clearly heals the spirit - a part of every one of us which is often neglected by medicine and science. Seeing the humor in our painful or emotional situations can free us from the chains we have built around ourselves, helping us to recognize that life is more than anger or pain or sorrow, but that it is full of humor and the contagious sound of laughter.