Solvents. Under this heading, those substances which are known to soften tissue will be considered.

Sodium hydroxide, up to a saturated strength, or an ointment of salicylic acid, 5 per cent. to 50 per cent., depending upon the density of the tissue to which it is applied, are the ones commonly used.

These two drugs have the power to macerate dry, hard tissues.

Experience is necessary for the proper use of tissue solvents as the length of time that they are allowed to act is of as much importance as the strength of the solution.

Sodium hydroxide solution can be instantly neutralized with any acid and for this reason is preferable.