The development of inhalation anaesthesia : with special reference to the years 1846-1900... / [Barbara M. Duncum].
- Duncum, Barbara M.
- Date:
- 1947
Licence: In copyright
Credit: The development of inhalation anaesthesia : with special reference to the years 1846-1900... / [Barbara M. Duncum]. Source: Wellcome Collection.
507/664 page 487
![Fig. 132.—REGULATING STOPCOCK AND MIXING CHAMBER OF HEWITT'S APPARATUS FOR NITROUS OXIDE AND OXYGEN, 1897 (see also Fig. 131) Arrows show the direction of oxygen and nitrous oxide flowing from the bags into OT, oxygen tube, and NOT, nitrous oxide tube, respectively, iv and iv', valves acting during inspiration. (Upper figure.) NOO. Orifice for nitrous oxide. OC. Chamber in which a small amount of oxygen was allowed to accumulate. OO. Ten small orifices for oxygen (three showing) ' any number of which may be opened by moving the inner drum [ID, lower^figure]. All the i o oxygen orifices are of the same size except the first, and by means of the supplementary stopcock, SS, this can either be made of the same size as the other 9 (1 st position of SS), or it can be made equal to the 10 orifices collectively (2nd position of SS), or to 20 such orifices (3rd position of SS).5 In its third position SS gave the administrator the equivalent of thirty oxygen orifices. IV. Inspiratory, and EV, expiratory valve (with chimney, C). PD. Partial diaphragm directing the patient's expirations towards EV. (Lower figure.) ID. Inner drum, revolving within the mixing chamber, with H. Handle and pointer, which passed over the index on the side of the mixing chamber (see upper figure). S. Slot in ID. When H was at its lowest point (cf. Fig. 131), air entered the mixing chamber through AH, air hole, and slot, S, and was breathed in and out through IV and EV, NOO and OO being closed by ID. As ID was revolved by raising H, AH closed and first NOO and then an increasing number of oxygen inlets, OO, were made to coincide with slot, S, thus allowing nitrous oxide and oxygen to enter the mixing chamber. By means of SS the equivalent of any number of oxygen orifices between one and thirty could be opened.](https://iiif.wellcomecollection.org/image/b20457200_0511.jp2/full/800%2C/0/default.jpg)
