Read the following passage and fill in each blank with ONE most suitable word. NOTHING'S NEW IN MEDICINE Throughout the ages, disease has stalked (0) our species. Prehistoric humans must quickly have learnt what could be eaten without danger, and how to avoid plants that could bring about illness. They found leaves, berries and the bark of different trees that could actually heal wounds and cure the sick, and (9) ______ soon became a special skill to understand natural medicine. Ever (10)______ the dawn of history, medicine men and wise women have always been expert in treating diseases and have dispensed medicine with ritual and magic. Through trial and error they discovered treatments for almost (11) ______ affliction prevalent at the time. The precious recipes for preparations which could relieve pain, stop fits, sedate or stimulate were (12) ______ down from generation to generation, although there was (13) ______ exact understanding of the way in which the medicines worked. Nevertheless, (14) ______ the power of these primitive medicines, generations were still ravaged by disease. During the last 150 years, scientists and doctors (15) ______ work has focused on these early medicines, have learnt that their power derived from certain chemicals which were found in herbal remedies or could be synthesised in the laboratory. In just such a way, advances in modern medicine continue, aided by the discoveries made centuries ago by our ancestors.