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250 DENTAL MEDICINE.
great degree of cold ; hence it has been employed in the form of
spray, as a local anaesthetic. It combines with alcohol and
chloroform in all proportions, and dissolves in ten times its
volume of water.
Medical Properties and Physiological Action.—Ether is a diffusible
stimulant, antispasmodic, anodyne and anaesthetic. Its action on
the animal organism is rapid and powerful, but temporary, and,
except for its rapidity, is similar to that of alcohol. When ap-
plied to the skin it produces intense cold by its evaporation, and
when applied in the form of spray it benumbs or locally freezes
a part.
Both the liquid and vapor act as an irritant to mucous mem-
branes, and its vapor when first inhaled causes great irritation of
the fauces and respiratory tract, often causing a temporary arrest
of respiration, the face becoming suffused and red and the con-
junctiva injected, such conditions causing restlessness and strug-
gling; but a quiet stage soon follows the primary stage. During
this second stage, the breathing is usually full and deep, and the
pulse rapid and strong, the ocular reflfexes at the beginning being
intact. The second stage may also be one of struggling, during
which the patient may become uncontrollable except by great force,
but if the inhalation be pushed a third stage of complete anaesthesia
is soon attained, when any surgical operation may be performed.
The inhalation should not be carried to complete flaccidity
of muscular contraction as the respiration may be obstructed.
Sulphuric ether first acts upon the brain, then upon the sensory
and motor tracts of the spinal cord, then on the sensory and
motor tracts of the medulla oblongata, and, if given to excess
it causes death from respiratory failure. It produces no effect
upon the nerve trunks unless it is directly applied to them. It
does not act by any destructive influence on the blood, but simply
suspends for a time the vital functions of the part which it effects.
It is one of the most diffusible and rapid cardiac stimulants, in-
creasing the pulse rate and force, and stimulating the heart and
the arterial pressure by accelerating the activity of vaso-motor
centres. In excessive doses it is a depressant of the heart, and
decreases the haemoglobin and the number of the red corpuscles,