![]() In 1824 Frenchman Henri Milne-Edwards suggested that the basic structure of all animal tissues was an array of "globules," though his insistence on uniform size for these globules puts into question the accuracy of his observations. Leeuwenhoek made numerous and detailed observations on his microorganisms, but more than one hundred years passed before a connection was made between the obviously cellular structure of these creatures and the existence of cells in animals or plants. It is likely that Leeuwenhoek was the first person to observe a red blood cell and a sperm cell. ![]() In 1676 the Dutch microscopist Antony van Leeuwenhoek (1632 –1723) published his observations of single-cell organisms, or "little animalcules" as he called them. While improvements in microscopy made their observations better, it was the underlying belief that there was some fundamental substructure that made the microscope the instrument of choice in the study of life. The prevalent view of Hooke's contemporaries was that animals were composed of several types of fibers, the various properties of which accounted for the differences among tissues.Īt the time, virtually all biologists were convinced that organisms were composed of some type of fundamental unit, and it was these "atomistic" preconceptions that drove them to look for such units. The presence of cells in animal tissue was demonstrated later than in plants because the thin sections needed for viewing under the microscope are more difficult to prepare for animal tissues. Grew likened the cellular spaces to the gas bubbles in rising bread and suggested they may have formed through a similar process. Marcello Malpighi (1628 –1694), and Hooke's colleague, Nehemiah Grew (1641 –1712), made detailed studies of plant cells and established the presence of cellular structures throughout the plant body. He did not propose, and gave no indication that he believed, that these structures represented the basic unit of living organisms. The open spaces Hooke observed were empty, but he and others suggested these spaces might be used for fluid transport in living plants. He made thin slices of cork and likened the boxy partitions he observed to the cells (small rooms) in a monastery. English physicist and microscopist Robert Hooke (1635 –1702) first described cells in 1665. The invention of the microscope allowed the first view of cells. So fundamental are these ideas to biology that it is easy to forget they were not always thought to be true. These simple and powerful statements form the basis of the cell theory, first formulated by a group of European biologists in the mid-1800s. History of Biology: Cell Theory and Cell StructureĪll living organisms are composed of cells, and all cells arise from other cells.
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