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644 LOCAL ANESTHETICS AND TOOTH EXTRACTION.

Inicclioiis forced Ix^twccii the periosteum and boiiu niuv produce
serious injury.
The iutroduetion of eucain as u loeul auesthetie was due to the
observed eheniieal siniiUirity of that synthetic body with cocaiu ; an
instance of presaging the physiological effects of a drug by its chemical
composition. Its local effect upon blooilvessels is to produce hyper-
emia, instead of the ischemia induced by cocaiu. It is less poisonous than
cocain and its solutions are chemically more stable. Its primary action
u])on the central nervous- system is one of exaltation, and this is followed
by paralysis, the effect being central, not ascending. The sedative
central iuHucuce causes a quickening of the heart-beats through sedation
of the inhibitory (pneumogastric) nerves. Although eucain is less toxic
than cocain it also produces a greater degree of analgesia ; so that the
dose need not be greater than that of cocain, about ^ to f of a grain
being the maximum.
Eucain may be kept in permanent and stable solution in distilled
water. A 10 per cent, solution may be made in distilled w^ater (48
grains of eucain hydrochlorid to the ounce of distilled water) and the
solution sterilized by boiling, which does not decompose eucain. From
five to eight minims of such a solution is a proper dose. The precau-
tions to be observed and the mode of application are the same as for
cocain.
Besides the dangers arising from the hypodermatic administration
of a physiological overdose of this class of analgesic drugs, and the local
danger of infection from non-sterile solutions or instruments, there is to
be strongly emphasized the danger of local necrosis due to the poisonous
effect of the drugs themselves upon the tissue elements when directly
injected. In nearly all cases in which extraction is sought the tissues
about the tooth are in a condition of lowered vitality, brought about by
the local toxemia resulting from the infection which has produced the
inflammatory process. The injection of a proto])lasmic poison, such as
cocain, eucain, and their congeners, into the inflamed territory causes a
still further depression of vital resistance, which, if sufficiently })ro-
nounced, may become total and permanent. Hence, tissue-death or
necrosis, with subsequent sloughing, will necessarily result.
AVhere the inflammatory process about a tooth is at all pronounced,
it is much Aviser to discard local anesthetic methods for the far safer
procedure of general anesthesia induced by nitrous oxid or ether.