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an instrument for cutting extremely thin sections of tissue for examination under an electron microscope.
The motion of the knife or the tissue is strictly regulated at a specific height in order to obtain sections that are usually not thicker than 200 angstroms (A) and are sometimes about 50 A thick. The thickness of a section depends on the quality of the fixing medium and the sharpness of the cutting edge of the knife. In most ultramicrotomes, the knife does not move, and the tissue is moved mechanically or, most often, thermally. The thermal mechanism, which was proposed in 1953 by F. Sjôstrand, operates on the basis of the controlled thermal expansion of the support rod to which the tissue is attached.
The USSR has developed an ultramicrotome based on the thermal mechanism that furnishes sections with a thickness of 50-800 A. Glass and diamond blades are used in ultramicrotomes. The quality of the blades is checked under a dark-field microscope, where the cutting edge of a blade of sufficient quality appears as a bright straight line.
REFERENCESElektronnomikroskopicheskie metody issledovaniia biologicheskikh ob”ektov. Moscow, 1963.
Weakley, B. S. Elektronnaia mikroskopiia dlia nachinaiushchikh. Moscow, 1975.
Sjôstrand, F. S. Electron Microscopy of Cells and Tissues, vol. 1. New York-London, 1967.
S. IA. ZALKIND