Bark (botany) rope, used for example in the rigging of Viking age longships. Among the commercial products made from bark are cork, cinnamon, quinine (from the bark of Cinchona) and aspirin (from the bark of willow trees). The bark of some trees notably oak ("Quercus robur") is a source of tannic acid, which is used in tanning. Bark chips generated as a by-product of lumber production are often used in bark mulch in western North America. Bark is important to the horticultural industry since in shredded form it is used for plants that do not thrive in ordinary soil, such as epiphytes.
Therapeutice Specialis ad Febres Periodicas Perniciosas who first systematically studied the effect of cinchona in the treatment of malaria, wrote a book which he titled "Therapeutice Specialis ad Febres Periodicas Perniciosas". One highlight of the "Therapeutice Specialis" is the drawing "tree of fevers", where different fevers, such as branches of the tree, are divided into categories: on the left, those that respond to cinchona, are shown as branches covered with bark, while on the right are those for which cinchona is ineffective, and are depicted as denuded leafless branches. Torti clearly identified cinchona as a specific therapy for intermittent fevers, as opposed to continued fevers, which