Turtles don’t have vocal cords and their ears are internal, so scientists believed that turtles were deaf and didn’t communicate through sounds. However, research has found that turtles actually communicate at an extremely low frequency that sounds like “clicks, clucks, and hoots” that can only be heard through a hydrophone (a microphone used underwater). These sounds even come from the egg before the turtle hatches. Researchers hypothesize that this helps all the turtle siblings hatch at once.
Pig bladders were used in the 19th century to store an artist’s paint. The bladder would be sealed with a string and then pricked to get the paint out. This option wasn’t the best because it would often break open. American painter John G. Rand was the innovator who made paint tubes from tin and screw cap in the 19th century.