Abstract
Avoidance of stain variation among mounted sections incubated in small volumes of fluid can be overcome by the construction and use of a microcell. Perspex rings of appropriate diameter are attached to small Perspex rectangles to form wells, small trip bars being also attached to the rectangles to simplify subsequent manipulation. The wells are filled with incubation fluid, and slides bearing frozen sections are held in position with small rubber bands. With certain dehydrogenases formazan production by this method is uniformly greater than that produced by incubation in drops of solution. In the case of the moderately active enzyme, 6-phosphogluconate dehydrogenase, the volume of the incubation mixture was not critical between 65 and 270 [mu]I.