"Friedrich Ludwig Kreysig (7 July 1770 – 4 June 1839) was a German physician born in Eilenburg.
In 1795 he received his medical doctorate from the University of Leipzig, and during the following year served as a substitute to Johann Gottfried Leonhardi (1746–1823) at the University of Wittenberg. In 1801 he became a professor of anatomy and botany at Wittenberg.
In 1803 he was appointed personal physician to Frederick Augustus, and from 1815 served in Dresden as a trainer of Saxon military doctors. Due to health reasons, he left academic work in 1822, retiring to a private practice, from which he concentrated on botanical studies." - (en.wikipedia.org 10.05.2020)