A Microscopic Method of Distinguishing Dead from Living Bacterial Cells.

Dilute solutions of dyes were applied to animal or plant cells nearly as far back as a century ago. By this means it was sought to gain an insight into various life processes of the cells, to demonstrate certain cellular structures, or to find out whether the cell were dead or alive. The work started by Ehrlich on nerve cells and blood cells, and the stimulus it gave other workers, have given us a respectable literature on the subject, to which contributions are still being made from time to time. The first application of "vital" stains to bacteria was made by Metchnikoff (1887) in his immortal study of phagocytosis. He says: