This substance is procured by making incisions through the bark of the
Norway Spruce fir, and afterwards boiling the flakes so obtained in
water, and then straining the resin through coarse cloths under a press;
whereas _frankincense_ (Abietis resina) is a spontaneous exudation from
it. It is now entirely confined to external use, as a rubefacient spread
on leather; it is very adhesive. _Emplast: Picis comp_. L. _Emplast:
Picis Burgund_. D. ADULTERATIONS. A factitious sort, manufactured in
England, is often met with; it is to be distinguished by its friability,
and its want of viscidity and unctuosity, and by the absence of that
peculiar odour which characterises the genuine specimens.