of lower end of humerus the relations of the epicondyles to radius and ulna are retained (Fig. 74).

Reduction of dislocation of the elbow backward (Hamilton).

Reduction is effected by sudden downward traction, sometimes necessarily preceded by forced extension of the forearm.

Discuss dislocation of the thumb.

The most common is that of the metacarpo-phalangeal joint, in which the phalanx is displaced backward and upward up over the head of the metacarpal bone. Reduction is effected by direct traction, preceded by hyper-extension if necessary. At times reduction is rendered impossible on account of the flexor brevis pollicis. The two tendons of insertion of this muscle are slipped back, one on each side of the head of the metacarpal bone, and thus embrace it, so tightly at times, that an open operation may be necessary in order to effect reduction (Fig. 75).

Discuss dislocation of the inferior maxilla.

The condyles, one or both, are usually displaced forward on one or both of the eminentiæ articulares. Reduction is effected by

Backward Dislocation of Proximal Phalanx of Thumb, showing metacarpal head thrust through and held by heads of short flexor muscle (Agnew).

pressing, with the thumbs in the mouth, against the coronoid processes downward and backward, while the rest of each hand, grasping the angles, presses forward and upward.

Backward dislocation is comparatively rare, and usually involves fracture of the external auditory meatus.

INFLAMMATIONS OF BONE.

Give a general description of bone inflammations.

The inflammations which attack bones are the same in every respect exudation, causation, etc.-as those which affect the soft parts. The apparent difference, as regards the actual lesion, is due entirely to the presence of the mineral salts, which mix with the ordinary products of inflammation and give them their characteristic

hardness or grittiness. Were it not for these salts the products of bone inflammation would be identical with those of cellulitis. Bone is, in fact, connective tissue, and the mineral salts are not to be considered as taking part in the inflammatory process. They are inert matter necessarily mixing with, as just said, the products of inflammation. For example: An acute bone inflammation kills an area of bone tissue by destroying its blood-supply, etc. Were there no mineral salts in this area, it would be absorbed or remain as a mass of gangrene or detritus, just as in acute cellulitis. But the salts in this area give it hardness and consistency sufficient to resist absorption, and thus we have remaining a mass of bone gangrene or necrosis. On the other hand, a chronic bone inflammation infiltrates a given area of bone tissue and destroys it in a molecular manner-breaks it up, as it were, instead of killing a large area at once. Similarly, absorption of this destroyed tissue would result as in cellulitis, but again the mineral salts share in this disintegration, and the result is a gritty mass of bone-particles which is called caries.

What is osteomyelitis ?

This is the general name for all varieties of bone inflammation. The marrow, hard tissue (compact and cancellous), and periosteum are the three elements of bone. It is found that they are all more or less involved in any bone inflammation, even when the process is chiefly located just beneath the periosteum. Hence the general name osteomyelitis. Periostitis, or inflammation of the periosteum, is really a superficial osteomyelitis, in which the periosteum also and necessarily takes a share.

What are the general varieties of osteomyelitis?

Osteomyelitis, like other inflammations, may be non-specific or specific, and each of these may in its turn be acute or chronic. Of the non-specific varieties, suppurative osteomyelitis is the most important.

Describe suppurative osteomyelitis.

This is generally acute. In this form it may extend throughout the entire bone or be circumscribed. If the latter it is usually limited more or less to the region of the epiphyseal line. It is then often called "epiphysitis," and is the form most common in children. "Epiphysitis" of the upper extremity of the femur rapidly involves the hip-joint unless promptly treated, and is often

known as "acute hip disease." In long bones the inflammation, when diffused, may occur "idiopathically," idiopathically," or as the result of a wound, especially compound fractures.

What is the course of acute suppurative osteomyelitis?

If untreated, the pus breaks through the bone, burrows through the soft parts, and reaches the surface. This may occur in more than one spot, and thus we have a series of sinuses. At the same time, in the bone itself more or less extensive areas of necrosis are formed. The process now becomes chronic suppurative osteomyelitis, and cannot be cured until the areas of necrosis are removed by operation.

What is the pathology of acute suppurative osteomyelitis?

It is practically that of an acute abscess (which see). The difference is due entirely to the peculiar structure of bone, and is essentially as follows: The "destructive inflammation" in an acute abscess, becomes in bone a rarefying osteomyelitis, which is the same process modified only by the fact of its occurrence in bone. Beyond this is, similarly, a "productive" bone inflammation or a sclerosing osteomyelitis, by which the bony tissue is thickened or increased in amount. Likewise in the centre is pus. Now, as the process advances, instead of there being a lot of detritus or brokendown tissue mingled with the pus, we have an area of necrosis, as already explained, around which the pus is extending. At the same time, the rarefying osteomyelitis beyond the pus gradually separates this area of necrosis from its connection with the rest of the bone, until finally this necrosed area becomes a separate movable mass which is called a sequestrum. The involucrum is simply the name given to the new bony tissue formed by the "sclerosing osteomyelitis." By this time the sinuses above referred to have formed, and the holes in the bone formed by the beginning of these sinuses are called cloaca. Should the process occur on the surface of a bone, superficial flakes of necrosis are formed, and there is little or no involucrum except what may be formed by a productive periostitis. The terms sclerosing and rarefying osteitis, or osteosclerosis and osteoporosis, are sometimes used. They simply mean sclerosing and rarefying osteomyelitis respectively.

What is the pathology of other forms of osteomyelitis?

In non-specific, acute, and non-suppurative there is simply an effusion of serum and fibrin, with, possibly, some rarefying and scleros

ing osteomyelitis, as secondary processes, the main process being called serous or simple osteomyelitis. It tends to resolution with or without the formation of necrosis. If the former, it is called "quiet necrosis," which is eventually absorbed by fatty degenera

tion.

Sclerosing and rarefying osteomyelitis may occur as primary processes. (See subjoined table of Bone Inflammations.)

Non-specific chronic osteomyelitis.-This may be serous or suppurative. If serous, it is simply the acute form become chronic, and if dead bone is produced, it is in the form of caries, which is similarly absorbed. If suppurative-this is much more commonit occurs in two forms: (a) as succeeding the acute after the formation of necrosis, sinuses, etc.; (b) as a primary process. In this case it is circumscribed, is at or near the epiphysis, and regular caries is produced. It is often called "chronic bone abscess." This process is the one which so often complicates or secondarily infects a focus of tubercular osteomyelitis. As a primary process it must not be confounded with this last.

The specific varieties of osteomyelitis, especially the tubercular and syphilitic, form each its own lesion in bone, just as they do in the connective-tissue planes, as already described. Here, again, we have the presence of the mineral salts mixed with the destroyed bone tissue, contributing to form caries. Thus we have a specific as well as a non-specific caries, each being the result of a corresponding chronic osteomyelitis. Either variety may occur deep in the bone or beneath the periosteum, in the latter case giving rise to "nodes," tubercular or syphilitic, as the case may be. At times syphilitic osteomyelitis may produce necrosis instead of caries, especially when seated in the bones of the skull. (See table for other varieties.)

What are the symptoms of osteomyelitis?

Non-specific Varieties.-The general symptoms are those of septicæmia, and they vary in severity according to that of the especial variety of osteomyelitis present. The local symptoms are pain in the bone, most intense of course when the inflammation is suppurative, and, as a rule, more severe at night; some enlargement of the bone. When sinuses form and reveal necrosis by means of the probe, the diagnosis is certain. The only difference between the acute and chronic varieties before the formation of sinuses is in the intensity of the pain and the severity of the septicemia.