From the book, The Healing Power of Humor, by Allen Klein

"Dr.John Diamond believes that smiling, or even looking at a smile, as Burgess did, gives us what he calls "life energy." "We have always known, "says Diamond, "how beautiful and beneficial a smile is. Now we can show-actually demonstrate-the therapeutic value of smiling." In his book "Your Body Doesn't Lie", he states that smiling helps strengthen the thymus gland, an important contributor to a healthy immune system, because the zygomaticus major (those smile muscles) and the thymus gland are closely linked."