Development of "the cell concept"
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Waddington (1968), for all his outstanding contributions to biology in the middle and later part of the 20th century, failed to mention the cell as a concept in his paper 'Main biological conceptions'. The cell to him was a reality, an object for investigation, a fact. Only such a fundamental notion can so present itself to one's consciousness that one considers it "something that goes without saying" - an objective phenomenon, like the sea or the stars. But the cell, a concept that took many years to emerge, was by no means an "obvious fact" to all concerned at the outset. The cell concept probably had a no less painful birth than many other concepts that now are considered fact, such as the heliocentric nature of our solar system (Galileo, 1612-32). That birth (not literally of the cell, but of the concept of the cell) has been the subject of much intensive research, compiled as one fascinating, highly erudite but complex treatise in Harris (2000). We might all concede that there is a "unit of life", and might be prepared to call it a cell, but there is no precise, unambiguous and generally agreed definition of "a cell". Science is a continuous process of refining and perfecting our own and other people's perspectives on a phenomenon; conceptions are replaced as further and better information becomes available. We slowly approach a consensus in this way. Few truths will endure through the sojourn of man or his successors on this planet, and many "truths" held today may be found inappropriate tomorrow. This progression from old to new continues, such that at present the cell remains a conception; but the object as such does not interest science, it is the explanation of the object that holds the interest. Our notion of the cell is in many respects as controversial today as it was centuries ago. If this statement holds true, then we should still find it very difficult, if not impossible, to define a cell. And if this in turn is true, then we must accept that the "cell" remains an abstraction, a hypothesis, or at most a young theory requiring further definition, and not a fact. This can more easily be appreciated by reviewing its development, but unfortunately few cell biologists, eager to make their mark in this highly competitive and rapidly advancing field today, seem to find the time to look at the history of its emergence. We hope, however, that they will browse this database and imbibe a little more about their inheritance. The cell is like a matryoskya, a Russian doll; it opens up in ever increasing numbers of smaller components; every year we learn of new parts, of metabolons, organelle components such as porosomes, and membrane rafts of which a full description would not have been possible a year or two earlier. Perhaps one day we will be able to define a cell; we might have a general formula that explains all parts of this remarkable operational system of life. A theory of everything wrapped up in a single equation by Feynman or Hawking may be on the cards in physics, but this is certainly is not the case in biology. Einstein warned us all about exploring the depth of living substance. To paraphrase his remarks, the complexity is far too great in all four dimensions - compared to matters with which we are familiar on a daily basis - to even contemplate the task. And as Schrödinger (1945) remarked, if we had started with biological systems, many physical laws today would look surprisingly different today. |
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