Page 626 - My FlipBook

624 EXTRACTION OF TEETH.

made to cover the nose as well as the mouth. The advautafi^e of the
first mouth-piece is that the lips may be closely watched I'or the change
of color denoting oxygen-starvation of the blood, which the experienced
operator combats by admitting a certain amount of air with the gas as
required. Fig. 567 represents a portable appliance to be used at a
patient's home or away from the regular office.

Fig. 567.

Portable nitrous oxid apparatus.
Dr. Hewitt's Method.—Dr. Frederick Hewitt of London, England,
has devised the apparatus shown in Figs. 568 and 569. The three
cylinders contain the compressed gas, two being filled with nitrous oxid
and one with oxygen. The valves of the cylinders are opened by a key
which is controlled by the foot of the operator. The tube passing from
the cylinders to the receiving-bag is double, a smaller tube being placed
within the outer larger tube. The receiving-bag is also double, being
divided by a rubber septum into two compartments W'hich have their
outlet in the double tube which leads to the inhaler. To the receiving-
bag is attached a mixing-chamber, and to this the inhaling-tube or hood
is fastened. This appliance is used very successfully in England and
has been introduced into the United States. It has proved satisfactory
to all who have tried it. The bags and tubing should be made of
more durable material when intended for use in the American climate.