This substance, commonly known as Barkstone, by trappers and
fur dealers, is obtained from the beaver, and is a remarkable aid in
the capture of that animal. It is an acrid secretion of a powerful
musky odor, found in two glands beneath the root of the tail of
the beaver. These glands are about two inches in length. They are
cut out and the contents are squeezed into a small bottle. When
fresh the substance is of a yellowish-red color, changing to a
light-brown when dried. Both male and female animals yield the
castoreum, but that of the male is generally considered the best.
Castoreum is a commercial drug, and in many beaver countries it
is quite an article of trade. There are other sacs lying directly
behind the castor glands which contain a strong oil of rancid smell.
This should not be confounded with the Castoreum.