1) Various enzymes as mineralization proceeds in the hetrotopic hard tissue formation were histochemically observed.
2) Alkaline phosphatase in the non-mineralized matrix shows a high activity, which quickly diminishes as mineralization occurs in the matrix. Cells, however, continue to show the activity.
3) Acid phosphatase shows strong activity in the non-mineralized matrix. The mineralized matrix also displays acid phoshatase activity at first, but is gradually reduced as calcification progresses.
4) Esterase activity is stronger in the mineralized matrix than in the nonmineralized matrix. In this experiment it did not reduce with the progress of mineralization.
5) Neither in the non-mineralized nor in the mineralized area, was succinic dehydrogenase activity observed in the matrix. In these areas it was observed only in the cellular element.
6) In the present experiment no aminopeptidase activity was observed in the tissue under mineralization.