This is a medical technique we still use today! Nobody likes to go through complicated or painful medical procedures, and so it helps to have something else to occupy our minds with when they're happening.
Almost everybody loves animals, and soft, cute ones are particularly popular with young children. Put a little pool full of ducks in front of an infant, and they won't even notice the medical equipment! We're not sure that the ducks would meet hygiene requirements in a modern hospital, though.