Theodor Schwann discovered pepsin, a gastric enzyme found in human stomachs that digests proteins. Theodor Schwann was a famous German physiologist who also coined the term "metabolism," and served as a human anatomy and physiology professor at the University of Leuven, Belgium in the early to mid-19th century.
Theordor Schwann was born in 1810. Known as a pioneer in the study of histology — the study of plant and animal tissues, Schwann largely contributed to the classification of human tissue types. His five-group classification of human tissues includes separate independent cells; compacted independent cells; cells with coalesced walls, such as bones and teeth; cells with formed fibers, such as ligaments and tendons; and cells that formed by syntheses of cavities and walls, such as muscles.
Through his study and classification, Theodor Schwann stumbled upon the inner workings of human physiology that allowed him to discover pepsin and the role that it plays in the breaking down of proteins within the human stomach. In 1879, Theodor Schwann was inducted into the Royal Society and the French Academy of Science for his long, continuing dedication to authenticating his scientific discoveries throughout his career. He died in 1882, two years after retiring from the scientific community.