inflammation of the surrounding skin,
and, if used near the eyes, may give rise to conjunctivitis. As a rule,
it should not be employed about the head. Moreover, it stains the linen
permanently and the skin temporarily.

_Pyrogallol_ is valuable, and is employed in the same manner and
strength as chrysarobin. In collodion it should at first not be used of
greater strength than three to four per cent., as in this form
pyrogallol sometimes acts with unexpected energy. It is less rapid than
chrysarobin, but it rarely inflames the surrounding integument. It
stains the linen a light brown, however, and is not to be used over an
extensive surface for fear of absorption and toxic effect. Oxidized
pyrogallic acid, a somewhat milder drug in its effect, has been highly
commended, and has the alleged advantage of being free from toxic
action.

_Tar_ is, all things considered, the most important external remedy. It
is comparatively slow in its action, but is useful in almost all cases.
As employed usually it is prescribed in ointment form, either as the
official tar ointment, full strength or weakened with lard or
petrolatum. It may also be used as pix liquida, with equal part of
alcohol. Or the tar oils, oil of cade (ol. cadini), and oil of birch
(ol. rusci) may be employed, either as oily applications or incorporated
with ointment or with alcohol. Liquor carbonis detergens, in ointment,
one to three drachms to the ounce of simple cerate and lanolin is a mild
tarry application which is often useful. In stubborn patches an
occasional thorough rubbing with a mixture of equal parts of liquor
carbonis detergens and Vleminckx's solution, followed by a mild
ointment, sometimes proves of value. In whatsoever form tar is employed
it should be thoroughly rubbed in, once or twice daily, the excess wiped
off, and the parts then dusted with starch or similar powder.

_Ammoniated mercury_ is applied in ointment form, twenty to sixty grains
to the ounce. Compared to other remedies it is clean and free from
staining, although, as a rule, not so uniformly efficacious. It is
especially useful for application to the scalp and exposed parts. It
should not be used over extensive surface for fear of absorption.

_[beta]-Naphthol_ and _resorcin_ are applied as ointments, thirty to
sixty grains to the ounce, and as they are (especially the former)
practically free from staining, may be used for exposed surfaces.

Gallacetophenone and aristol also a