Abstract
Model experiments with serum-gelatine pieces in which the effect of some basic histotechnical procedures on the phosphatase activity was studied, are reported. Following fixation and dehydration in alcohol, clearing in methyl-benzoate-celloidin, and embedding in paraffin at temperatures up to 53°C., the phosphomonoesterase activity was preserved, while embedding at higher temperatures caused increasing inactivation. The admixture of slight amounts of "soft paraffin" (m.p. 42°C.) to the ordinary 55° paraffin and embedding at 52-53° is advocated for phosphatase studies.