nown. It exists in varying, though small proportion, in all
species of tobacco. Those called mild, and most esteemed, seem to
contain the least. Thus, according to Orfila, Havana tobacco yields two
per cent of the alkaloid, and Virginia nearly seven per cent. In the
rankest varieties it rarely exceeds eight parts to the hundred. The
same toxicologist says that it has the remarkable property of resisting
decomposition in the decaying tissues of the body, and he detected it in
the bodies of animals destroyed by it, several months after their death.
In this particular it resembles arsenic.

_Nicotianin_, or the volatile oil, is probably the odorous principle of
tobacco. According to some, it does not exist in the fresh leaves, but
is generated in the drying process. When obtained by distillation, a
pound of leaves will yield only two grains; it is therefore in a much
smaller proportion than the alkaloid, forming only one half of one per
cent. It is a fatty substance, having the odor of tobacco-smoke, and
a bitter taste. Applied to the nose, it occasions sneezing, and taken
internally, giddiness and nausea. It is therefore one of the active
constituents of tobacco, though to a much less degree than nicotin
itself. For while Hermstadt swallowed a grain of nicotianin with
impunity, the vapor of pure nicotin is so irritating that it is
difficult to breathe in a room in which a single drop has been
evaporated.

When distilled in a retort, at a temperature above that of boiling
water, or burned, as we burn it in a pipe, tobacco affords its third
poison, the _empyreumatic oil_. This is acrid, of a dark brown
color, and having a smell as of an old pipe, in the pores of which,
particularly of meerschaum clay, it may be found. It is also narcotic
and very poisonous, one drop killing reptiles, as if by an electric
shock: in this mode of action it is like prussic acid. But this
empyreumatic oil consists of two substances; for, if it be washed with
acetic acid, it loses its poisonous quality. It contains, therefore, a
harmless oil, and a poisonous alkaline substance, which the acetic acid
combines with and removes. It has been shown to contain the alkaloid
nicotia, and this is probably its only active component.

Assuming, therefore, that nicotianin, from its feebler action and small
amount, is not a very efficient principle in producing the narcotic
effects of tobacco, and that the empyreumatic oil consists only of fatty
matters ho