It must first of all be remembered what was said of joints, articulations, and ligaments in the first lecture under that head. We must thence observe, that a dislocation of the upper arm with the shoulder is the most common that happens, because of the great variety of motion, and the flatness of the head of the arm-bone, and the cavity of the shoulder blade. Next to this is the thigh bone, with the hip. But this is done by much greater force, and therefore more troublesome in reducing. All other joints that are angular are seldom really dislocated, being stronger secured, and cannot be separated from their articulation, without first tearing the ligamentous capsula that surround them; yet nevertheless, some are subjected to be partly dislocated; and this is what is commonly called sprains. Dislocations may be from two causes; first from violence, secondly from weakness of the ligament. In the latter case the reduction is the easiest, but the limb is apt to slip out again by the least accident.[11] Footnote 11: I remember a man who frequently had his shoulder dislocated, and was his own operator in reducing it again. The first time the accident happened in the ship I was surgeon of, I was naturally called to his assistance: “Stop Doctor,” (said Tom) “I have got a tackle in my chest, and I will soon bouse it in again;” and sure enough, he had a pully, with which he immediately reduced it. I shall briefly consider each kind of dislocation, that an accident makes a man liable to. _Dislocation of the Arm with the Shoulder._ The dislocation of that, may be two ways; (viz) downwards, and forwards; but it cannot be backwards nor upwards; except some part of the shoulder-blade be broke.——The best method to examine the patient what kind of dislocation it is, (especially to one unacquainted with these branches of surgery) is strictly to compare both shoulders, and the difference will be very plain, both to sight and touch. If the dislocation is downwards that is, the head of the arm-bone, slipt in the arm-pit, there will be a cavity on the top of the shoulder, different from the sound arm, and the elbow will be drawn upwards, without being able to be moved either towards the body; or so, as the patient to put his hand out without the greatest pain.