The Histochemical Test for Alkaline Phosphatase

Abstract

WE should like to direct attention to the occurrence of a phenomenon of diffusion in the histochemical technique for the demonstration of alkaline phosphatase which makes precise localization of the enzyme difficult and is apt to produce errors in interpretation. With regard to such possible diffusion, two opposing views have been taken. Danielli¹, on the basis of specially designed experiments similar to, but not identical with, some of those to be reported here, has denied such diffusion (that is, of the reaction product) and declared the method as very reliable with regard to the localization of the enzyme. Lison², on the other hand, takes—at least with certain tissues—the occurrence of diffusion (that is, of enzyme) for granted and makes bad histological fixation responsible for it. There is abundant evidence in the literature in the form of photomicrographs, tabulated records, and descriptions of positive reactions given by cell constituents, especially nuclei, in the vicinity of regions of high phosphatase activity which makes the existence of diffusion as a complicating factor very likely ; yet positive proof has so far been wanting. The following experiments seem to furnish such proof.