SELECTED ARTICLES. 11 
in closely stopped vials, excluded from the light and heat, it 
loses its potency. It possesses so penetrating, and strong a 
smell of mustard, as to produce a painful sensation in the nose 
and eyes, with an increase of secretion, and so powerful is it, 
that when brought in contact with the sound skin, intolerable 
heat and burning, with intense redness and vesication, are the 
result. Hence, if used for medicinal purposes, it must be in a 
most dilute form. For external application, thirty drops 
may be dissolved in an ounce of spt. vini, or six or eight 
drops in a drachm of ol. amygdalae, which solutions have 
still the characteristic odor and taste. There are two modes of 
external application. First, one of the above preparations may 
be rubbed on the skin by means of a piece of flannel or linen 
dipped in it; this method answers well in general, especially 
in the cases of children and females, and upon places where the 
skin is tender and not impaired in sensibility. The solution, 
thus applied, evaporates in a few minutes, leaving a sensation 
of burning and redness; parts contiguous to those affected are to 
be selected, and the application may be repeated after in- 
tervals of from four to six hours. 
2. Pieces of flannel or linen, moistened with the solution, 
may be applied and retained in their position, until the active 
principle evaporates, which occurs generally in eight minutes. 
This method is suited to patients with a less irritable skin, or 
in whom the sensibility has been impaired by disease. The 
burning sensation immediately is experienced, and sometimes 
becomes intolerable, the patient tearing off the pledgets, under 
which the skin appears still more reddened and even blistered. 
In chronic cases it is sufficient to make the application twice 
a day, but not over the same places, from the excessive irrita- 
tion. 
As the effect of this essential oil upon the human system 
is so energetic, it is only calculated to be employed as a contra- 
irritant in diseases without excitement, as in chronic rheuma- 
tism, and affections of joints, its attendants, where it presents 
some advantage over blisters. It will, likewise, prove ser- 
vicable in neuralgia, odontalgia, paralysis, &c, in which the 
