Woodcut of a method of bloodletting among Native Central American Indians. An Indian maiden is being bled from tiny puncture wounds inflicted by another Indian using an arrow. Bloodletting was based on an ancient system of medicine in which blood and other bodily fluid were considered to be "humors" the proper balance of which maintained health, but it often weakened sick patients. It was the most common medical practice performed by doctors from antiquity up to the late 19th century, a time span of almost 2,000 years. This image has been color enhanced.