 Complete the following phrase:  Willow bark preparations became a standard part of the materia medica of Western medicine beginning at least with the Greek physician Hippocrates in the fifth century BCE; he recommended chewing on willow bark to relieve pain or fever and drinking tea made from it to relieve pain during childbirth. The Roman encyclopedist Celsus, in his De Medicina of ca. 30 AD, suggested willow leaf extract to treat the four signs of inflammation: redness, heat, swelling and pain. Willow treatments also appeared in Dioscoridess De Materia Medica, and Pliny the Elders Natural History. By the time of Galen around the year 200 C.E., willow bark was commonly used throughout the Roman world and later after the 