The most poisonous animal in the world is probably the two-toned arrow-poison frog – only 28 grams (1 ounce) of its poison could kill nearly 3 million people.
During heart surgery in 1970, a patient with haemophilia (an inherited condition which stops the blood clotting) needed 1,080 litres of blood – nearly 15 baths full – as he kept bleeding.