This depends on the condition of the bill. In normal used condition, they are worth exactly $2. $2 bills dated 1976 and newer are the ones worth face value only. The $3/$4 figure is reasonable for bills dating back to the 1950s.
Klein thought he had, discovered the poison to be due to a disease of the cow. An epidemic of scarlet fever broke out in London in December, 1885, and the outbreak could be traced to the milk supplied by a herd in Hendon.
U.S. Army Physicians Discovered the Cause of Yellow Fever. August 27, 1900. With doctors at a loss as to how to stop the spread of yellow fever, people tried all sorts of strange remedies. They burned barrels of tar in the street to disinfect the air. They sprayed sulfur and lime mixtures into homes of the infected.