_Gutta-Percha_ may always be substituted for leather in these splints, and the same plan of fitting is used, except that the notching requisite in leather is not necessary in using gutta-percha; for the directions to use this material see page 50. CHAPTER IV. DISLOCATIONS. The main obstacles in reducing dislocations are entanglement together of the displaced bones and contraction of the muscles; the entanglement of the bones determines the direction in which extension must be made, and also of the _counter extension_, or point at which the body is fixed to resist the traction practised on the limb; this should be exactly opposite the direction in which the limb will be drawn. The muscles can always be relaxed by chloroform, hence it is better when they are powerful, not to use the limb as a lever to prize the head of the bone into its place. Steady extension instead is better, to disengage the bone from the parts against which it is caught, and to bring it opposite its socket, into which the hands of the surgeon guide it with less risk of laceration of the soft parts than attends forcible leverage. =Lower Jaw.=—This bone is dislocated on one or both sides; when the condyle has slipped forward from the glenoid fossa, the contracted temporal muscle keeps the bone from regaining its proper position, and causes the coronoid process to hitch against the malar bone. _Treatment._—_Apparatus._—1. A towel. 2. A four-tail bandage. [Illustration: Fig. 60.—Dislocation of the jaw.] The patient should be seated in a high-backed chair, resting his head against the back. The surgeon winds the towel round both thumbs, and standing immediately in front of his patient, places a thumb on the second molar of both sides, if the dislocation be double, or on one side only, if that be alone displaced (see fig. 60). He then presses steadily downwards until the condyle is released, when it slips back to its place. The return of the bone may be aided by pushing up the chin with the fingers _after_ the ramus of the jaw has been lowered. When the jaw is replaced, a four-tail bandage or split handkerchief should be tied over the nucha and vertex of the head, to keep the jaw closed (see fig. 23, page 32). Biting or chewing should not be attempted for ten days or a fortnight. The patient should be warned also that when the jaw has been once dislocated it very readily slips out of place again; he must thenceforth avoid gaping or opening the jaw very widely. =The Clavicle= is rarely dislocated, nevertheless both the inner and the outer end may be displaced. The signs are obvious—the end of the bone is felt in its new position. The treatment for all is the same. _Apparatus._—1. Roller, 2¼ inches wide. 2. A piece of old blanket.