They are very astringent, haemostatic and sedative; the strong solution of the subacetate is powerfully caustic and is rarely used undiluted.
It is a powerful local haemostatic, but it only checks haemorrhage when brought directly in contact with the bleeding point.
Medicinally, gallic acid has been, and is still, largely used as an astringent, styptic and haemostatic. Gallic acid, however, does not coagulate albumen and therefore possesses no local astringent action.
So far is it from being an haemostatic that, if perfused through living blood-vessels, it actually dilates them.
This action on the vessels is so marked as to constitute the drug a haemostatic, not only locally but also remotely.