Morphine, like many prescription drugs, may require larger doses for pain control when used for extended periods of time. Over time, the body can develop a tolerance for the medication and will require more medication to experience the same level of effectiveness.
By Kimberly Munro Fri, Mar 18, 2011. The first installment of our Ancient Peru series relates what archaeology has revealed about its first cities and civilizations. The expansive, culturally rich civilizations that existed in the Americas at the time of European contact came as a great surprise to the early Spanish explorers. Most notable were the Aztec empire in Central Mexico and the Incan empire in Peru, both of which controlled great expanses of land and millions of people.
The Mayan people did not disappear and continue to live in Mexico and Central America. The Aztecs. The Aztecs were a people who came into the Valley of Mexico in the 12th century and quickly rose to become the dominant power in Mesoamerica. The capital of the Aztecs, Tenochtitlan, was built on Lake Texcoco on raised islands. The Aztecs formed an empire commanding tribute from other city states in Mesoamerica.