2. A fracture of the condyle may sometimes arise from a _counter-stroke_, as when, in consequence of some external force being applied from before backwards, and from below upwards against the chin, this process is driven against the projecting rim of the glenoid cavity; at other times it may be the effect of an immediate or direct stroke, as when a body in motion strikes with force against the region of the joint, and does violence to that portion of the bone. 3. But in whatever manner the fracture may be produced, it generally occurs in the slender part of the bone which supports the condyle, below the insertion of the pterygoideus externus. It is characterized by a pain more or less acute, necessarily accompanying the motions of the jaw; by a difficulty more or less considerable, in the performance of these motions; by a crepitation, oftentimes distinct, when, in consequence of the angle of the jaw being pushed forward, or the jaw itself alternately depressed and elevated, the separated surfaces rub against each other; by an inequality of surface sometimes perceptible directly over the fractured condyle; by the ease with which, on being pushed forward, it may be forced into the depression beneath the zygoma; and by its remaining stationary, during the movements of the lower jaw, from which it is separated. These signs, though generally characteristic, are subject to an uncertainty proportioned to the swelling that occurs in the part. 4. In this accident a displacement is almost always produced by muscular action. The pterygoideus externus, being attached to the condyle, draws it forward and upward, towards the external wing of the pterygoid apophysis, its fixed point of insertion. On the other hand, the body of the bone is left behind, being held by the masseter and external pterygoid muscles, the course of which is opposed to a displacement in the same direction; so that there always exists a separation, more or less perceptible, between the two fragments of bone. 5. Hence, if proper means be not used to restore the contact between the broken ends of the bone, the following consequences will be likely to occur: 1st. Their reunion will be tedious, because in every bone this process is, in point of rapidity, inversely proportioned to the separation of the divided surfaces: 2dly, This reunion may even entirely fail to take place, if the bone be subject to the slightest movements, as I have witnessed in a particular case, where the condyle, not being reunited to the other part, exfoliated, and was in part discharged through the external integuments: 3dly, Under such circumstances, the callus produced in the process of healing, being situated near to the joint, and rendered irregular and deformed by the separation of the parts, is apt to impede muscular action, and do a permanent injury to the functions of the jaw. § III.