Abstract
The intensity of the color reaction obtained in certain tissues with the periodic acid Schiff (PAS) technique can be diminished by fixatives containing formalin. Hydrolysis of these tissues by NaOH before oxidation in PAS will produce a strength of color reaction comparable to that obtained in those tissues not fixed in formalin. The relationship between formalin fixation, alkaline hydrolysis, and the chemical configuration of PAS positive substances is discussed.