The German biologist Theodor Schwann (1810-1882) is considered a founder of the cell theory. He also discovered pepsin, the first digestive enzyme prepared from animal tissue, and experimented to disprove spontaneous generation. Theodor Schwann was born at Neuss near Düsseldorf on Dec. 7, 1810.Click to see full answer. In this way, what is Theodor Schwann best known for? Lived 1810 – 1882. Theodor Schwann was an anatomist and physiologist who is best known for developing the cell doctrine that all living things are composed of cells. Schwann discovered the enzyme pepsin and discovered glial cells in nerves – these are now known as Schwann cells.Also Know, how did Theodor Schwann die? Stroke what did Schleiden do? Matthias Jacob Schleiden (1804–1881) Schleiden studied cells as the common element among all plants and animals. Schleiden contributed to the field of embryology through his introduction of the Zeiss microscope lens and via his work with cells and cell theory as an organizing principle of biology.What did Schleiden and Schwann propose?By the late 1830s, botanist Matthias Schleiden and zoologist Theodor Schwann were studying tissues and proposed the unified cell theory. The unified cell theory states that: all living things are composed of one or more cells; the cell is the basic unit of life; and new cells arise from existing cells.