Math Science Chemistry Economics Biology News Search
A matter open to endless discoveries
Nowadays with the term cell we mean the elementary particles of every living being with a cellular structure able to feed and reproduce itself. Researches are still being carried out that will lead to a thorough definition of the cell.
But how have we reached the modern conception of cell? The first person to observe and describe the cell was the English scientist Robert Hooke; he was a versatile man and was considered one of the greatest scientists of the 17th century. He was the first to use a compound microscope (made up of a cylindrical body and a biconvex lens) to examine all sorts of objects: especially pieces of thin cork. Noticing that these samples, made up of a network of empty spaces, resembled the rooms where the monks lived in the monasteries, the scientist coined the term cell. Hooke observed the cell but he did not understand the meaning of it.
In the same period the Dutch, Antoni van Leeuwenhoek, unlike Hooke, set his attention on simple microscopes. He built an excellent simple microscope that allowed him to obtain bigger enlargements. he used some powerful lenses of good quality to get these results but it was difficult to handle and to keep it in focus; To overcome this drawback he arranged the sample to observe on top of a grapevine, being able to adjust with care their distance from the zoom-lens. The observer had to hold the instrument next to the eye and look through the lens. With this microscope he studied especially the nervous system cells and he understood that the structure of the peripheral nerves was consisted of countless extensions of the nerve tissue. He observed, drew and described a multitude of bacteria, in particular the bacteria of saliva and pound water.
The first modern ideas about cells appeared around the beginning of 19th century when, by using optical microscopes, scientists were able to observe the cell in detail. In fact, the optical microscope exploits a source of light to analyse the tissue sample. It is also made up of a combination of two convergent lenses (the zoom and the ocular lens).
Those were set at a fixed distance from the stage on which the sample is set. Using this microscope scientists got some remarkable enlargements of the analyzed sample and they understood the difference between the nucleus and the cytoplasm since they exploit a colouring technique which consists in dipping the sample to be analyzed into a dye, called ematossilin, which colours the nucleus; then the sample is dipped in natural water and the colour ranges from deep purple to blue; finally the sample is dipped into another dye called eosin that colours the cytoplasm. This method also made it possible to observe in detail the cellular division and especially the differences between mitosis and meiosis.