Principles and practice of operative dentistry . nger signals. In the latter instrument the face-piece or hoodis a serious disadvantage, in that it covers the mouth and nose, making itimpossible to watch the effects of the gas upon the blood, while in thosepatients who wear a beard it is impossible to exclude the admission of , as in cases of harelip, or when the orbicularis oris musclesare so much swollen that it is impossible to close the lips about the mouth-piece, the hood becomes of great service. Fig. 651 shows the mechanismof the inhaler. Hewitts Method—Sir Frederick Hew
Principles and practice of operative dentistry . nger signals. In the latter instrument the face-piece or hoodis a serious disadvantage, in that it covers the mouth and nose, making itimpossible to watch the effects of the gas upon the blood, while in thosepatients who wear a beard it is impossible to exclude the admission of , as in cases of harelip, or when the orbicularis oris musclesare so much swollen that it is impossible to close the lips about the mouth-piece, the hood becomes of great service. Fig. 651 shows the mechanismof the inhaler. Hewitts Method—Sir Frederick Hewitt, of London, England,believing that the symptoms of asphyxia which so often accompany theadministration of nitrous oxide gas might be overcome by the admixtureof a proper amount of oxygen with the gas, devised an apparatus bywhich oxygen can be mixed with the gas in various proportions. The apparatus (Fig. G52) consists of three cylinders of compressed gas,two filled with nitrous oxide and one with oxygen, the valves of which are Fig. under the control of the foot of the operator. Connecting the cylinderwith the rubber inhaliug-bag, which is divided into two compartments bya rubber septum, is a double tube for conveying the gases to the bag. Tothe upper end of the inhaling-bag is attached a mixing-chamber, and tothis is attached the mouth-piece or inhaling-tube. When about to administer the gas, the valves of the mixing-chamber ANAESTHETICS, LOCAL AND GENERAL. 667 Fig. 653.
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Keywords: ., bookcentury1900, bookdecade1920, booksubjectdentist, bookyear1920
