Conrad Gessner occupation physician
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Conrad Gessner was a Renaissance polymath, a physician, philosopher, encyclopaedist, bibliographer, philologist, natural historian and illustrator. In 1537, at the age of 21, his publication of a Graecolatin dictionary led to his sponsors obtained for him the professorship of Greek at the newly founded academy of Lausanne (then belonging to Bern). Here he had leisure to devote himself to scientific studies, especially botany, and earn money to further his medical studies.
After three years of teaching at Lausanne, Gessner was able to travel to the medical school at the University of Montpellier, where he received his doctoral degree (1541) from Basel. He then returned to Zürich to practice medicine, which he continued to do for the rest of his life.  There he was also appointed to the post of lecturer of Aristotelean physics at the Carolinum, the precursor of the University of Zürich.
After 1554 he became the city physician (Stadtarzt). In addition to his duties there, and apart from a few journeys to foreign countries, and annual summer botanical journeys in his native land, and illnesses, he was able to devote himself to research and writing. His expeditions frequently involved visits to mountainous country, below the snow-line. Although primarily for purposes of botanical collection, he also extolled mountain climbing for the sake of exercise and enjoyment of the beauties of nature. In 1541 he prefixed to his treatise on milk and milk products, Libellus de lacte et operibus lactariis a letter addressed to his friend Jacob Avienus (Vogel) of Glarus on the wonders to be found among the mountains, declaring his love for them, and his firm resolve to climb at least one mountain every year, not only to collect flowers, but in order to exercise his body. In 1555 he issued his narrative Descriptio Montis Fracti sive Montis Pilati of his excursion to the Gnepfstein (1920 m), the lowest point in the Pilatus chain.Gessner is credited with a number of the first descriptions of species in Europe, both animals such as the brown rat (Rattus norvegicus), guinea pig (Cavia porcellus) and turkey (Meleagris), as well as plants such as the tulip (Tulipa gesneriana). He first saw a tulip in April 1559, growing in the garden of the magistrate Johann Heinrich Herwart at Augsberg, and called it Tulipa turcarum, the Turkish tulip. He is also credited with being the first person to describe brown adipose tissue, in 1551, in 1565 the first to document the pencil, and in 1563 among the first Europeans to write about the effects of tobacco.
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