A substrate-film method for the histochemical demonstration of cellulase

Summary A substrate-film method has been devized for the histochemical demonstration of cellulase. The substrate film is made of sodium carboxymethyl-cellulose, which is made insoluble in water by fixation in acid ethanol. The tissue is briefly fixed in cold formalin, washed, and sectioned with a freezing microtome. The sections are mounted on slides, and covered with a piece of carboxymethyl-cellulose film, and the slide is incubated in a warm, moist atmosphere. After incubation, the film is stained with toluidine blue, and sites of cellulase activity appear as pale or clear patches in the film.In the digestive systems of certain molluscs, cellulase has been found in the lumens of the crop and stomach, and in the lumen and absorptive cells of the digestive gland tubules. The salivary glands, and the epithelia of the crop and stomach, show no reaction.Sections of control tissue, inactivated by boiling in water, do not show any reaction.I thank the Nobel Division of Imperial Chemical Industries Ltd. for information on their product Cellofas B 10, and for permission to publish that information.