DEVICE FOR OPTICALLY DETERMINING MICROBIAL COLONY POPULATION ON GROWTH SURFACE

摘要

A viewer-comparator device is described for optically determining the density of microbial colony growth in and on an inoculated nutrient layer. In the preferred construction the device comprises a base, a magnifying lens supported thereon, means connected to the base for supporting a nutrient layer-coated surface, this surface being located in position for viewing thereof through the lens, means to enable direct visual comparison by an observer between the appearance of the nutrient layer-coated surface and reproductions of microbial growth at a plurality of representative intervals over a range of growth densities of clinical interest and lighting means depending from the base. The comparison enabling means is located adjacent the position to be occupied by the nutrient layer-coated surface for simultaneous viewing of both the comparison enabling means and the coated surface through the lens. The lighting means are so directed that light rays emanating therefrom cannot pass to the lens by reflection or by direct passage from lighting means to lens. With the lighting means so disposed and directed, the microbial colonies will scatter the light reaching them and appear bright in an essentially dark field (i.e. no bright background).