Sources : Tysus

Thomas of Cantimpré [circa 1200-1272 CE] (Liber de natura rerum, Serpents 8.40): Tysus is a serpent of the Paduan mountains, six or seven feet in length, thin, but much thicker at the back than at the front. It has a short and pointed tail about the length of a palm. It walks on its belly, having ribs which visibly move like feet it relies on when running. Its course is swift, its leap is inestimable. When it runs or walks, it holds its head and neck up to its belly, and its ribs erect in a lofty position. It does no harm to anyone unless he is severely infected. It has two red lines on its back. Its rotten flesh is mixed with fish makes a drink against leprosy, which is frequently a most effectual remedy. - [Badke translation/paraphrase]