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328 DENTAL MEDICINE. ;

CHLORIDE OF METHYL—METHYL CHLORIDE.
Formula.—CH3CI.
Derivation.— Chloride of Methyl is produced by the action of
chlorine upon marsh gas ; by heating together common salt,
sulphuric acid and methyl alcohol -, or it is more cheaply manu-
factured by using the waste products of beets used in the manu-
facture of sugar. It is the chloride of a hydrocarbon in the form
of methyl chloride, and resembles ether in appearance, taste and
smell, but is less inflammable. Chloride of Methyl is generally
employed as a local anaesthetic in the form of spray, although it
possesses general anaesthetic properties also, and being very
volatile and ether-like, rapid evaporation occurs when it is
applied over an effected area. To avoid producing inflammation
of the skin, or an erythema in persons having an irritable skin,
caution is necessary ; and it should be applied over as many
nerve filaments as possible. The special advantage of chloride
of methyl is its external application, which may never cause
more than a temporary irritation of the skin. In order to
produce local anaesthesia with this agent, M. Bardet proposes
before spraying a surface with it, to paint it with glycerine, the
revulsive action being less severe, and the glycerine forming a
surface on which the drops of the refrigerant mixture collect, and
which may be readily removed after the desired effect has been
produced ; the use of glycerine is also said to prevent the dangers
of sloughing. Dr. Ch. Bailly recommends the following method
of applying this agent as a local anaesthetic A tampon of dry
:
cotton covered with dry silk is sprayed with the anaesthetic until
its temperature is reduced to 23^-55° C. below zero. The
tampon is then grasped with ebony pincers and applied for a few
seconds to the parts to be anaesthetized, and perfect abolition
of pain at once secured. Drs. Daboll and Rhein recommend
chloride of methyl as an application for trigeminal neuralgia,
giving immediate relief by paralyzing the small filaments of the
nerve. The spray is also used for obtunding sensitive dentine
it produces a more intense cold than ether, and with less pain,
its obtunding effect lasting a longer time.