9. But whatever may be the causes or kind of the luxation, its diagnosis is always easy. If it be forward, the direction of the stroke which the shoulder has received, furnishes, at first, some ground of suspicion. The accident is certainly known by the appearance of a hard and unnatural protuberance in front of the sternum, and behind the extremity of the sterno-cleido-mastoideus muscle, by the existence of a sensible depression or hollow at the joint, and by the situation of the shoulder, which is pushed further backward, and is less projecting and more approximated to the trunk, than in its natural state. Add to these, a difficulty in performing motions in a forward direction, which, when somewhat forced, reduce, in proportion as they are accomplished, the size of the protuberance formed by the displaced end. The head is always inclined towards the side where the luxation exists; an attitude which relieves the painful drawing or tension produced in the sterno-mastoideus muscle, by the humeral extremity pushing it forward. 10. A protuberance over the superior edge of the sternum, a difficulty in raising the shoulder, the pain which results from attempting such a motion, the diminution of the protuberance which it occasions, the absence of the sternal extremity from its natural cavity, the approximation of the shoulder to the thorax, and its depression and diminished projection, compared to its usual state, afford evidence of a luxation upwards. 11. A luxation inward or backward, would be characterized by a projection of the shoulder exteriorly, by a difficulty in performing motions in a backward direction, by the alarming effects, which, as Petit remarks, the compression of the trachea would doubtless produce, and by a depression or hollow at the joint, more perceptible here than in the two preceding cases. 12. These appearances will be more or less striking, accordingly as the membranes, lacerated or only distended, offer a greater or less resistance. § IV. OF THE REDUCTION. 13. To reduce a luxation, is, in general, to make the bone re-enter its cavity, by retracing, or returning along, the same route which it followed in escaping from it. Now, in a forward luxation, the displacement is from behind forward, in an upward one from below upward, in an inward or backward one from before backward, but, in each of the three, it is more particularly from without inward. In the first case, therefore it is backward, in the second, forward, in the third downward, but, in each of the three, more particularly outward, that the powers for producing extension must be directed.