The first of these arises very generally from a fall on the point of the shoulder, and as in such a case, the commotion or shock must be very great, to extend with sufficient force through the thick mass which forms the deltoid muscle, that muscle sometimes suffers both contusion and an echymosis. Blood may even escape from a rupture of some of the arteries or veins of the joint, and form, as Desault has observed, a collection or tumour which it would be imprudent to open. The other is the effect of a fall on the elbow, separated, at the time, some distance from the trunk, or on the hand, which, by a natural instinct, is thrown out, together with the arm and fore-arm, in order to break the violence of the fall. 4. The varieties of this kind of fracture originate, 1st, from the spot which it occupies, being either the middle or the lower part, rarely the upper part, of the neck of the humerus: 2dly, from the state of the surrounding soft parts, which sometimes remain quite natural, and at other times become distended and tumefied. This circumstance always involves the diagnosis in more or less uncertainty; 3dly, from the direction of the fracture, which is sometimes transverse, but usually oblique, particularly when produced in the second mode, that is, by a counter-stroke (3); 4thly, from the relative situation of the fragments, which may remain in contact, an occurrence however but very rare, or may separate from one another in a direction inwardly or upward; and, 5thly, from different complications, with which it may be attended. § III. OF THE SIGNS AND THE DISPLACEMENT. The whole of the signs of a fracture of the neck of the humerus, taken together, characterize its existence in a manner sufficiently evident. But it is not always an easy matter to take a view of them all at once, and in such a case, there are more difficulties attending the diagnosis here, than in any other fracture of the humerus. An acute pain is felt at the instant of the fall; and sometimes a crack or report is plainly heard. There is always a sudden inability to move the limb, which, being left to itself, hangs motionless. But if any external force act on it, it yields to it without resistance, and may be moved by it with great ease in every direction. These motions are accompanied with severe pain, and, if carried too far, may give rise to very troublesome affections, as has been observed in patients, where the fracture was mistaken for a luxation.