True because of supply and demand. If the demand is higher than the supply, or people cannot afford the supply, the demand must decrease in value so that people can facilitate the supply and keep it going.
At Jefferson's request the two houses of Congress considered and passed the Embargo Act quickly in December 1807. All U.S. ports were closed to export shipping in either U.S. or foreign vessels, and restrictions were placed on imports from Great Britain.
I believe the answer to this question
With the invention of the stethoscope, physicians were able to listen to the various sounds made by the heart and lungs. And began to be able to identify if patients had any diseases or ailments.