II.

Historical Origins of Cell Biology

The idea that cells are the fundamental building blocks of living organisms—sometimes termed “the cell theory”—is now universally accepted as true. However, this concept did not spring into existence fully formed, as the result of a single discovery. It took many years for the present view of cells to emerge, and there were many false turns and misapprehensions on the way. The word “cell” comes from the Latin cellula, meaning a small room or cubicle, and was first used by Robert Hooke in his book Micrographia, published in 1665. Hooke was describing the air-filled spaces of dead cells in a slice of cork (bark from an oak tree) and certainly did not realize the general importance of his discovery. Nor did many other talented microscopists of the 17th and 18th centuries, such as Antoni van Leeuwenhoek, Nehemiah Grew, Marcello Malpighi, and Jan Swammerdam, who also saw cells in plant or animal tissues, or as free-living organisms. Indeed it was not until 1839 that the combined insight of a botanist, Matthias Schleiden, and a zoologist, Theodor Schwann, led them to pronounce that “…all organisms are composed of essentially like parts, namely of cells”.

The cell theory was still far from complete and many curious notions remained, for example, about the origins of cells. It required the work of many other biologists, such as Bartholemy Dumortier and Robert Remak, to establish the fact that all cells are produced as a result of the division of existing cells. This notion, which has powerful implications for both cell biology and the origins of life, was famously articulated by German biologist Rudolph Virchow in the phrase “Omnis cellula e cellula”, that is, “all cells come from cells”.

Even then, many misconceptions still existed regarding the nature of the cell membrane, the cytoplasm, and the hereditary material, and it was not until well into the 20th century that the contemporary view of cells emerged. Indeed, even today, the amazingly complex internal structure and chemistry of living cells is still not fully understood and contains many secrets yet to be discovered.