Hematology

The scientific examination of blood in order to learn more about the health of the patient from whom it was taken can be dated to 1642, when Anthony van Leeuwenhoek first observed blood cells through his newly invented microscope. Progress was at first slow, and it was not until 1770 that leucocytes were discovered by William Hewson, an English surgeon, who also observed that red cells were flat rather than spherical, as had earlier been supposed.

Association of blood cell counts with clinical illness depended on the development of a technical method by which blood cells could be counted. In 1852, Karl Vierordt at the University of Tübingen developed such a technique, which, although too tedious for routine use, was used by one of his students, H. Welcher, to count red blood cells in a patient with "chlorosis" (an old word for what is probably our modern iron-deficiency anemia). He found, in 1854, that an anemic patient had significantly fewer red blood cells than did a normal person. Platelets, the third major cellular constituent of blood, were identified in 1862 by a German anatomist, Max Schultze.

Remarkably, all these discoveries were made without the benefit of cell staining, an aid to microscopic visualization that was not introduced until 1877 in Paul Ehrlich's doctoral dissertation at the University of Leipzig. The movement of blood cell studies from the research laboratory to routine support of patient care needed a fast automatic technique for separating and counting cells, which was eventually provided by the Coulter brothers, Wallace and Joseph. In 1953 they patented a machine that detected the change in electrical conductance of a small aperture as fluid containing cells was drawn through.

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Project Management Made Easy

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