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396 DENTAL MEDICINE.
" spray apparatus," which should furnish enough of the liquid to
moisten the skin. The extremity of the tube should be held
some two or three inches from the surface on which the spray is
to be thrown. Within two or three minutes after its first appli-
cation, anaesthesia of the part occurs, which is shown by the ap-
pearance of a white spot. The formation of this spot may be
hastened by superficially puncturing or scratching the skin. The
sensation of cold thus produced is sometimes disagreeable, but
is rarely painful.
Given internally it is also said to relieve gastric pain without
affecting the appetite. Inhalations have been used to relieve
convulsive cough ; and, introduced on cotton wool into the ex-
ternal meatus, it is said to relieve the pain of otalgia, without
causing any irritation.
EUCAINE.
Formula.—C^gH^NOiHCiH^O.
Derivation.—Eucaine is an artificial alkaloid produced by the
reaction between acetone (dimethyl ketone, CH3COCH3), and
ammonia. Two chemical substances having the name of Eucaine
have been introduced, each of them depending for its anaesthetic
property upon the presence of the benzoyl molecule in its con-
stitution. They are called, AIpha-Eucaine and Beta-Eucaine.
Although Alpha-Eucaine was the substance usually sold under
the name of Eucaine, yet it is as poisonous as cocaine, while
Beta-Cocaine is not, cocaine being three times more toxic. The
use of Alpha-Cocaine has been almost entirely discontinued.
The salt principally employed is the hydrochlorate which, when
evaporated from the aqueous solution, retains one molecule of
water of crystallization.
Hydrochlorate of eucaine is in the form of a white, odorless
crystalline substance, or powder of a bitter taste like that of
quinine, and soluble in water, chloroform and alcohol.
Medical Properties and Action.—Eucaine, when applied locally',
induces some hyperemia of the mucosae, rather than anemia, but,
nevertheless, causes a very decided loss of sensibility. It has a
marked advantage over cocaine in being less poisonous, although