THE HIPPOPOTAMUS.
This beast when it feels itself over-full goes about seeking thorns, or where there may be the remains of canes that have been split, and it rubs against them till a vein is opened; then when the blood has flowed as much as he needs, he plasters himself with mud and heals the wound. In form he is something like a horse with long haunches, a twisted tail and the teeth of a wild boar, his neck has a mane; the skin cannot be pierced, unless when he is bathing; he feeds on plants in the fields and goes into them backwards so that it may seem, as though he had come out.
THE IBIS.
This bird resembles a crane, and when it feels itself ill it fills its craw with water, and with its beak makes an injection of it.
THE STAG.
These creatures when they feel themselves bitten by the spider called father-long-legs, eat crabs and free themselves of the venom.
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.