The Wet-film Indian Ink Method for examining Micro-organisms

RECENT experience with the wet-film indian ink method, used by Duguid 1 for demonstrating bacterial capsules and slime, suggests that it can be used for examining the structure of a wide range of living micro-organisms. To be effective for this purpose, an ink should have very small, uniformly sized particles, should spread evenly and should not coagulate too readily. These requirements are met by ‘Pelican’ black drawing ink, though it does coagulate to some extent in acidic suspensions. Several other inks proved unsatisfactory, chiefly because of larger and more variable particle-size.