iS6 OPERATIVE TECHNIQUE. 



The most generally useful, however, are planter and tvipoliih 

 baiidai^cs. Modellers' dr}^ plaster is rubbed into ordinary loosely 

 woven bandages which are then rolled up, care being taken that as large 

 a quantity as possible of the plaster is retained in the material. Just 

 before use they are saturated with water (preferably containing a little 

 dissolved alum, which hastens setting) ; they are then gently squeezed 

 and at once applied to the parts, which have previously been padded 

 as above described. The first folds should be applied around the free 

 extremity of the limb and bandaging continued upwards, care being 

 taken not to use much pressure. The piece of linen placed next the 

 skin should extend beyond the limits of the bandage so that when the 

 latter is complete the edges of the linen can be turned up after the 

 manner of a cuff, enveloping the wadding or other padding material. 

 This gives the dressing a rounded edge, and prexents any pressure on 

 or rubbing of the skin. After complete application the surface of the 

 dressing may be smoothed with the wet hands, or some thin plaster 

 may be spread over it and smoothed off. Depending on its thickness 

 the bandage sets in from tifteen to thirty minutes, during which time 

 extension or flexion of the limb must be prevented. Plaster of Paris, 

 if long kept or allowed to become damp, sometimes fails to set, but a 

 little care in storage will prevent this. If desired, setting may be 

 delayed by adding glycerine to the water used in mixing the plaster. 

 To further support the dressing thin pieces ot wood or splints of zinc 

 or tinned iron may be inserted between the layers. 



Hertw^ig suggests oiling the skin, and slipping over the limb 

 an arrangement resembling the leg of a pair of drawers into which 

 thin plaster is poured. This might certainly be tried under very 

 special circumstances, and would appear to promise security 

 against irregular local pressure, but though attractive in theory would 

 probably prove extremely difficult to carry into practice. Moreover, 

 should swelling tend to occur at any point the unyielding character of 

 the dressing might cause very serious results. 



Instead of pure plaster a mixture of one part cement to two or 

 three parts of plaster has been recommended. It appears to present 

 no special advantages. 



Tripolith, a grey powder of unknown composition, is sold com- 

 merciail)'. It hardens in much less time than plaster, and has the 

 advantage of keeping well, even in open vessels. Dressings made with 

 it are lighter and cheaper than those made with plaster, but as it 

 hardens so very rapidly only one or two bandages should be moistened 

 at a time. 



All the above dressings can be made waterproof by varnish or shellac 



