Frequency of bowel movements varies widely among individuals, as well as varying widely for any single individual. In studies on the subject, approximately 50 to 70 percent of people surveyed report having a single daily bowel movement. Outliers range from one movement every three days to three movements a day.
Cell theory was eventually formulated in 1839. This is usually credited to Matthias Schleiden and Theodor Schwann. However, many other scientists like Rudolf Virchow contributed to the theory. The three tenets to the cell theory are as described below: All living organisms are composed of one or more cells.
Theodor Schwann Theodor Schwann (7 December 1810 â 11 January 1882) was a German scientist who isolated and named the enzyme pepsin. He also played a key role in promoting the idea of the cell as the foundation of living organisms. His work on the cell has recently been re-assessed, because the idea had been discussed before him. Cell history