The Da Vinci Notebooks at sacred-texts.com
This has two heads, one in its proper place the other at the tail; as if one place were not enough from which to fling its venom.
This lies on trees, and flings itself down like a dart, and pierces through the wild beast and kills them.
The bite of this animal cannot be cured unless by immediately cutting out the bitten part. This pestilential animal has such a love for its mate that they always go in company. And if, by mishap, one of them is killed the other, with incredible swiftness, follows him who has killed it; and it is so determined and eager for vengeance that it overcomes every difficulty, and passing by every troop it seeks to hurt none but its enemy. And it will travel any distance, and it is impossible to avoid it unless by crossing water and by very swift flight. It has its eyes turned inwards, and large ears and it hears better than it sees.