There has been a considerable and increasing interest in the phosphatase problem for more than 15 years, as evidenced by the great number of papers published on it throughout the world. I n 1939 two practically identical methods for the demonstration of phosphatase in microscopic sections were developed simultaneously but independently by Takamatsu and Gomori. Both methods are based on the fact that phosphatase is well preserved by alcohol fixation (Martland and Robison) and by subsequent embedding in celloidin or paraffin. If sections of such alcohol fixed material are immersed in a properly buffered solution of any suitable ester-phosphate substrate and calcium ions are added, a precipitate of calcium phosphate will be formed at the sites of phosphatase activity. No precipitate of calcium phosphate will be formed if either the substrate or the calcium salts are omitted from the incubating mixture, as shown by Takamatsu. No precipitate will be obtained if the section is exposed before incubation to inactivating agents, such as water at 70Β°C. for 15 minutes, dilute mineral acids, silver salts and so on. On the other hand, definite intensification of the reaction will occur if any soluble magnesium salt is added to the incubating mixture, the optimal magnesium concentration being around N/lOO. These facts show the strict specificity of the reaction.
The results obtained with the routine chemical methods of phosphatase determination (e.g., that of Kay) are in excellent agreement with those of microtechnical visualization, as can be seen by comparing the data presented in this paper with those published by MacFarlane, Patterson and Robison, and by Truhlar. and his associates. Attention