An electron microscope study of the surfaces of normal and malignant cells in culture.

A certainamountof evidencehas accumulated in recent years (1, 92,3, 6, 7) which suggests that normal and malignant cells differ in their adhesive and other surface properties and, therefore, in the actual chemical composition of their surfaces. Dif ferences in structure, which might be associated with a chemical difference, are not immediately apparent in electron micrographs of sectioned cells. Malignant cells appear to be enclosed by a plasma membrane, seen as a dense line less than 100 A thick when viewed at low resolution, essen tially identical with that enclosing normal cells. There is, to judge from the number of intercellular gaps in such sectioned material, no lack of evi dence to support the view that the membranes of malignant cells are more active and less adhesive than those of normal cells, but the resolution is such that little can be asserted concerning the