Walther Flemming | Biography

Of Flemish descent, Flemming was born in Sachenberg, Germany, where his father worked as the director of an insane asylum. As a young man, Flemming showed great aptitude for literature and language, but chose instead to study medicine at several German universities. He served briefly as a hospital assistant before becoming an assistant in the department of zoology at Wurzburg University. In 1872, he accepted a position at the University of Prague, but the rise of Czech nationalism among his colleagues and students compelled him to return to Germany. He eventually became professor of anatomy and director of the Anatomical Institute at the University of Kiel, where he remained until his retirement.

Prior to Flemming's work, little headway had been made in the field of cytology since Matthias Schleiden and Theodor Schwann had proposed their cell theory in 1839, due in large part to the lack of effective cell staining techniques and poor microscopes. However, during the 1850s, advances in synthetic dyes were made, allowing scientists such as Flemming to better study cells. By using the new dyes, Flemming was able to observe and correctly identify the stages of cell division, a process that he later named mitosis.

Flemming found material within the cell nucleus that readily absorbed dye. He named the material chromatin, and by observing it at different phases, he could trace the action of cell division. As the process began, the chromatin arranged itself into short, thread-like objects, which Wilhelm von Waldeyer-Hartz later termed chromosomes. The chromosomes then doubled and pulled apart, each half migrating to opposite ends of the cell. In the final stage, the cell divided, leaving two daughter cells with equal amounts of chromatin.

By the end of 1879, Flemming had investigated all the stages of mitosis--a term that he derived from the Greek word for "thread"--and identified them in a variety of tissues. In 1887, he began concentrating on cell division in spermatozoa. Although he detected that differences existed in the way sex cells divided, Flemming failed to identify the process later termed meiosis by Edouard van Beneden.

Unfamiliar with the work of Gregor Mendel, Flemming was unaware of the genetic significance of his findings. However, with the rediscovery of Mendel by Hugo de Vries at the turn of the century, Flemming's work has since provided the physical basis for Mendel's theories of inheritance. Flemming's Zellsubstanz, Kern, und Zeltlteilung (1882; Cytoplasm, Nucleus, and Cell Division) is considered a classic text by cytologists.