21. There are more living organisms on the skin of a single human being than there are human beings on the surface of the earth. 22. From the age of thirty, humans gradually begin to shrink in size. 23. Your body contains enough iron to make a spike strong enough to hold your weight. 24. The surface area of a human lung is equal to that of a tennis court. 25. Most people have lost fifty per cent of their taste buds by the time they reach the age of sixty. 26. The amount of carbon in the human body is enough to fill about 9,000 'lead' pencils. 27. One square inch of human skin contains 625 sweat glands. 28. When you blush, your stomach lining also reddens. 29. The human body has less muscles in it than a caterpillar. 30. If you could save all the times your eyes blink in one life time and use them all at once you would see blackness for 1.2 years! 31. The life span of a taste bud is ten days. 32. It's impossible to sneeze with your eyes open. 33. Give a tennis ball a good, hard squee ze. You're using about the same amount of force your heart uses to pump blood out to the body. 34. The aorta, the largest artery in the body, is almost the diameter of a garden hose. 35. Capillaries, on the other hand, are so small that it takes ten of them to equal the thickness of a human hair. 36. Your body has about 5.6 liters (6 quarts) of blood. This 5.6 liters of blood circulates through the body three times every minute. 37. The heart pumps about 1 million barrels of blood during an average lifetime--that's enough to fill more than 3 super tankers. 38. Babies start dreaming even before they're born. 39. The human body can function without a brain. 40. Humans are the only primates that don't have pigment in the palms of their hands.