Under this division, we have to consider the two earths, _Lime_ and
_Baryta_; both of which are highly corrosive, although they essentially
differ from each other in their physiological action. In this respect
they may be compared to _corrosive sublimate_ and _arsenic_, and offer
an additional illustration of the imperfection of the present
classification; for while _lime_ acts as a local caustic upon the parts
with which it comes in contact, _baryta_ will require, for its action,
to be absorbed and carried into the current of the circulation.