The Use of a Chloral Hydrate Formaldehyde Fixative Solution in Enzyme Histochemistry

trimmed to a standard thickness (5 mm.) and taken from animals of the same age, weight and sex, were placed in each fixative previously chilled at 8#{176}C. Two fixative solutions were used. “Formalin-saline” (FS) was a mixture of 20 ml. of formaldehyde (Merck Neutral Reagent Grade 38.0%) and of 80 ml. of 0.9% sodium chloride in distilled water. “Chloral-formahin” (CHF) was a mixture of 20 ml. of formaldehyde and 80 ml. of distilled water. To this, 100 mg. of chloral hydrate (Merck, IT.S.P.) was added. Both fixative solutions were stored in bottles containing mari)le chips. The pH is slightly acid to litmus paper. A series of frozen sections from the same block1 were prepared at approximately 3 day intervals6 until the enzymes showed signs of deterioration or poor localization. Incubation periods for hydrolysis were kept constant for each method for purposes