Infiltration of a porous hard tissue with methyl methacrylate, followed by dissolution of the tissue provides a three-dimensional methacrylate cast of spaces within the tissue. Examination of such a cast by scanning electron microscopy provides information on the nature and extent of the pore system to a degree that cannot readily be visualized by the direct examination of fractured surfaces. The findings described concern human dentine but the technique may have a wider application in studies on the internal structure of other hard tissues.

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Abstract. Observations were made of changes in red cell morphology in blood stored in acid citrate dextrose over a period of six weeks using the scanning electron microscope. It was found possible to demonstrate the various stages of red cell transformation from biconcave discs, through a crenated stage to the final spheroidal state. Adenine was shown to slow down these changes. It is postulated that the red cell membrane changes are reversible up to the stage of the crenated spheroid cell, but subsequent changes result in a rapid destruction of the cell if transfused. The scanning electron microscopy studies can, therefore, be a useful method of observing the effect on red cell shape of new anticoagulants, red cell storage procedures and biochemical changes.