Matthias schleiden biography summary organizer

JMS Pearce
Hull, England

Every schoolchild is taught in biology about cells and their elemental importance. Students of biological and medical sciences also learn about the Schwann cell sheath that invests nerve fibers. What is less well known is how these two are related. Schwann, a physician by training, and Schleiden, a botanist from Hamburg, were the founders of the original concept of cell theory, the fundamental scientific basis of biology. This concept stated that cells are the structural and functional units of all living organisms, forming tissues, organs, and the entire plant or animal.

Cell theory had its roots in the physicist and astronomer Robert Hooke’s first depiction published in Micrographia in 1665. Before Hooke, in the seventeenth century, all living forms were thought to depend on vitalism. A force distinct from all physical and chemical forces peculiar to living organisms, vitalism controlled form and function. Living forms and their cells arose from spontaneous generation (abiogenesis) or from a pre-existing form (preformationism).

Hooke’s Micrographia contained a collection of copper-plate illustrations of many objects he had seen with his own compound microscope, including the porous cells of Quercus suber, the cork tree (Fig 1). He stated:

… these pores, or cells…were indeed the first microscopical pores I ever saw, and perhaps, that were ever seen, for I had not met with any Writer or Person, that had made any mention of them before this…

In 1670, Antony van Leeuwenhoek built a simple one-lens microscope and observed single-celled bacteria, which he reported to the Royal Society as animalcules. He also observed protozoa, plant cells, algae, blood cells, and living sperm cells. In his time, simple and compound microscopes developed and improved; scientists driven by curiosity used them to examine the structures of diverse living and non-living objects. Schleiden and Schwann rejected preforma

Abstract

The cell is not only the structural, physiological, and developmental, but also the reproductive unit of life. So far, however, this aspect of the cell has received little attention by historians and philosophers of biology. I will argue that cell theory had far-reaching consequences for how biologists conceptualized the reproductive relationships between germs and adult organisms. Cell theory, as formulated by Theodor Schwann in 1839, implied that this relationship was a specific and lawful one, i.e. that germs of a certain kind, all else being equal, would produce adult organisms of the same kind, and vice versa. Questions of preformation and epigenesis took on a new meaning under this presupposition. The question now was whether cells could be considered as independent agents producing adult organisms of a given species, or whether they were the product of external, organizing forces and thus a stage in the development of the whole organism only. The question was an important one for nineteenth-century biology. As I will demonstrate, it was the view of cells as independent agents which helped both Charles Darwin and Gregor Mendel to think of differential reproduction as a lawful process.

Keywords: Cell theory, epigenesis, preformation, specificity, Darwin, Mendel

1. Introduction

The cell is habitually addressed as the structural, functional, and developmental unit of life. Jan Sapp has aptly and succinctly explained these aspects of the cell by formulating “three tenets” of cell theory: “that all plants and animals are made of cells, that cells possess all the attributes of life (assimilation, growth, reproduction), and that all cells arise from division of preexisting cells” (Sapp, 2003, p. 75; cf. Reynolds as well as Nicholson, this issue). This misses an important fourth sense in which the cell can be regarded as a “unit of life”. The cell is also the reproductive unit of life, not in t

In 1665, Robert Hooke published Micrographia, a book filled with drawings and descriptions of the organisms he viewed under the recently invented microscope. The invention of the microscope led to the discovery of the cell by Hooke. While looking at cork, Hooke observed box-shaped structures, which he called “cells” as they reminded him of the cells, or rooms, in monasteries. This discovery led to the development of the classical cell theory.

The classical cell theory was proposed by Theodor Schwann in 1839. There are three parts to this theory. The first part states that all organisms are made of cells. The second part states that cells are the basic units of life. These parts were based on a conclusion made by Schwann and Matthias Schleiden in 1838, after comparing their observations of plant and animal cells. The third part, which asserts that cells come from preexisting cells that have multiplied, was described by Rudolf Virchow in 1858, when he stated omnis cellula e cellula (all cells come from cells).

Since the formation of classical cell theory, technology has improved, allowing for more detailed observations that have led to new discoveries about cells. These findings led to the formation of the modern cell theory, which has three main additions: first, that DNA is passed between cells during cell division; second, that the cells of all organisms within a similar species are mostly the same, both structurally and chemically; and finally, that energy flow occurs within cells.