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Figure 2–7. Cells from different organisms with defined nuclei (After Schwann, 1839; From Katznelson, 1963). 1 — gill cartilage from a frog; 2 — cartilage from a bone in the loins of a pig embryo; 3 — enamel fibres from the teeth of a pig embryo; 4 — cells from the surface of the enamel coating; 5 — fibres from a human tooth isolated by maceration with HCl; 6 — fibrous cell from a cell wall; 7 — better developed cells from a cell membrane; 8 — cells from the mucous substance of the membranes of a pig embryo; 9 — cell from the orbital cavity of a pig embryo; 10 — mast cells from the skull cavity of a fish; 11 — cells from the Achilles’s tendon of a pig embryo; 12 — cells from the middle layer of pig embryo aorta; 13 — muscle cells of a pig embryo.
Later Concepts on the Structural Organizacion of the cell. Discovery of Some Its Organelles
Section 2.3. The cell theory has confirmed the principle of uniformity in the
structure of plant and animal organisms. The cell was accepted as a basic
structural unit. The problem of the formation of new cells from the already
existing ones i.e. their genesis has come into the limelight.
An answer to this very important question was attempted to be given
by M. Schleiden and Th. Schwann. Schleiden has created the theory of
cytogenesis which is expressed in short by the following: from the mucous
substances attached to the inner layer of the cell wall of the existing cells,