Cohn, the first scientist to define and systematically classify bacteria, is considered a founder of modern bacteriology. He is also noteworthy for providing critical support to others in the fledgling science, including the Nobel Prize-winning Robert Koch.

Born to Jewish parents in 1828 in the Prussian city of Breslau (now Wroclaw, Poland), Cohn was a child prodigy reportedly able to read and write before his second birthday. He was admitted to the University of Breslau at the age of 14, but because of anti-Semitic feelings in Prussia, he was never granted a degree there even though he successfully undertook four years of studies.

Instead, Cohn completed his studies at the University of Berlin, where he studied under the prominent physiologist Johannes Peter Müller. When revolution swept Europe in 1848, Cohn kept his liberal tendencies to himself and kept involved in his studies. In September, 1849, he wrote a rather anguished...