Cell Theory

In the year 1838, a German botanist called Matthias Schleiden discovered that all plant tissues are made up of different types of cells. A British Zoologist, Theodore Schwann, who was a contemporary of Schleiden, reported the presence of athin outer layer in the animal cells which is now known as the plasma membrane.  Schwann also discovered that along with plasma membrane,an additional unique outer layer is also found exclusively in plant cells i.e. the cell wall. Both Schleiden and Schwann together postulated the Cell Theory, based on their findings. However, this theory did not give any indication of the genesis of cells.

In 1855, a German biologist named Rudolf Virchow first explained the origin of cells from pre-existing cells. This led to the modification of the original cell theory proposed by Schleiden and Schwann which is today understood as:

  1. All living organisms are made up of cells and cell products.
  2. Every cell is made up of pre-existing cells.