Abstract: | The binding of positively charged, colloidal ferric oxide particles to the surfaces of Ehrlich ascites tumour cells, before and after incubation with neuraminidase and/or ribonuclease, has been studied by electron microscopy. An attempt has been made to correlate the amount of binding observed, with the electrophoretic mobilities of the cells under similar conditions to those under which they were exposed to the ferric oxide. Although a progressive loss of staining was observed with progressive loss of cellular net surface negativity, neither property was predictable from knowledge of the other. Some of the difficulties inherent in quantitative staining techniques of this type are discussed. |