ACUTE ARTHRITIS 365 the same character as the latter, or metastatically in different acute infective diseases (pyæmia, typhoid fever, scarlatina, and so on), in which case it is excited by the specific micro-organisms of the primary infective disease or its complications. Hence pyococci are most frequently found in this kind of osteitis also, though in the osteitis and periostitis which often occur in the course of typhoid fever, typhoid bacilli, alone or in association with pyococci, may be the cause of the inflammation. The histological processes in secondary osteitis are in general not different from those of the primary form. Acute inflammation of the joints may also be primary or secondary. The former occurs as the so-called articular rheumatism (acute polyarticular rheumatic arthritis), and is not improbably always due to bacteria. It usually affects several joints, and gives rise to either a serous, a fibrinous, or a purulent exudation. In the serous exudation no micro-organisms have as yet been found, but in the others it has been possible to demonstrate the Diplococcus pneumonia and the pyococci. Acute articular rheumatism in its further course tolerably often leads to an acute endocarditis. An acute arthritis may also occur after injuries, should the bacteria of pus at the same time gain entrance. Another disease belonging to the primary form of acute inflammation of joints is uratic arthritis [gout], which most frequently affects the metatarso-phalangeal joint of the great toe and the finger joints, and is characterised by mortary-looking deposits of sodium or calcium urate in the cartilage, bones, and soft parts [tophi]. In the cartilage it is chiefly the cells and their capsules in which the urates are precipitated, in the form of stellate tufts of crystals, whereas in the soft parts the interstitial substance is also affected. Uratic arthritis may also take a more chronic course. The secondary form of acute arthritis occurs either by extension of an inflammation from the neighbourhood, e.g., in acute infective osteomyelitis, or (which is most frequent) metastatically, as happens in pyæmia (including puerperal fever), scarlatina, measles, cerebrospinal meningitis, gonorrhoea, and so forth. Metastatic arthritis may attack one joint or several, and is usually of a suppurative nature. It is, of course, excited by the micro-organisms of the primary diseased condition or of its complications. The histological changes in the primary and secondary forms of acute arthritis are the same. In slighter degrees the synovial membrane is found to be alone affected, its villi especially being enlarged by vascular dilatation and moderate small-celled infiltration; but in the severer degrees and when the disease is of longer duration, especially in the suppurative form, all parts of the joint are sympa FIG. 184.-SUPPURATIVE POLY ARTHRITIS (KNEE-JOINT). X 95. (Alum cochineal.) a, Synovial villi, swollen and infiltrated with cells; b, Necrotic parts in the synovial membrane; c, Aggregations of cocci. FIG. 185.-SWOLLEN SYNOVIAL VILLUS OF THE KNEE-JOINT IN SUPPURATIVE POLYARTHRITIS. X 545, the cocci drawn in under a power of x 975. (Weigert's modification of Gram's method.) a, Mononuclear and polynuclear leucocytes on the surface of the villus, with streptococci in and between them; b, Round cells in the villus; c, Swollen or newly-formed connective-tissue cells of the villus; d, Blood-vessel filled with streptococci, in the neighbourhood of which the cells have stained badly, indicating commencing necrosis. CHRONIC OSTEITIS AND ARTHRITIS 367 thetically involved. It is then found not only that the epithelium of the synovial membrane is cast off, the surface of the latter and its villi covered, and their tissue infiltrated, with mononuclear and polynuclear leucocytes (Fig. 185, a and b), whilst the tissue is even necrotic in places (Fig. 184, b, and Fig. 185, d), but that the cellular and purulent infiltration extends into the fibrous capsule of the joint, or even into the periarticular connective tissue. In the articular cartilage the active processes fall more into the background. Growth of the cartilage-cells and penetration of puscorpuscles into the cavities of the cartilage may indeed take place, but in most cases it is by degeneration or necrosis that the cartilage is destroyed, its interstitial substance undergoing a finely-granular clouding, or becoming fibrillated, as a preliminary to complete solution. The cartilage may also die en masse over considerable areas, whereupon its cells lose the power of staining; or it may be pressed upon and absorbed by the synovial membrane growing into it from the margin. After the destruction of the cartilage the inflammation may also extend to the bone. Should recovery take place at this stage, regeneration of the destroyed articular cartilage does not follow, but the articular ends of the bones become coated with granulation tissue, which develops from the synovial membrane and the tissue of the medullary spaces in the bone, and acquires connections by means of processes with the like tissue covering the opposed articular surface. Subsequently it passes through the process of transformation into connective tissue, with the result that a fibrous adhesion is formed between the two articular surfaces (fibrous ankylosis). If, however, ossification of this connective tissue sets in, an osseous ankylosis is the result. Of the chronic inflammations of bone most prominence must be given to that caused by inhalation of the vapour of phosphorus, and to the tubercular and syphilitic varieties. The first attacks the jawbones as a rule, leading partly to new formation of bone from the periosteum and marrow, and partly to suppuration, by which a more or less extensive necrosis of the bone, even of that newly formed, is caused. Regarding tubercular and syphilitic osteitis, see p. 372 et seq. Amongst the chronic inflammations of the joints we reckon first of all arthritis deformans (chronic rheumatoid arthritis). Its occurrence is conditioned above all by advanced age, but we also find it as a so-called trophic neurosis in diseases of the spinal cord accompanied by paralysis, especially in tabes; as the result of certain influences, traumatic and possibly rheumatic, which cannot be more accurately defined; and, lastly, also after too prolonged rest of a joint. Two forms of arthritis, a monarticular and a polyarticular, may LANE LIBRARY. STANFORD UNIVERSITY α be distinguished. The former affects chiefly the large joints, one only, or at least but few, being involved, and most frequently the knee or hip. The second form, however, affects many joints, and first those of the fingers and toes, especially in women; but it may then extend to other joints also (arthritis nodosa). Both forms are in general distinguished by the fact that in them those retrograde and hyperplastic changes, which have already been described (pp. 356 and 362) as appertaining to advanced life per se, attain an especially high degree of development. In the polyarticular form (Fig. 186), however, it is the proliferative FIG. 186.-ARTHRITIS DEFORMANS, POLYARTICULAR FORM. X 285. (Hæmatoxylin and eosin.) a, Growing synovial membrane overspreading the surface of the articular cartilage; b, Pitted depressions on the surface of the cartilage; c, Enlarged cartilage cavities, both occupied by cells having numerous processes; d, Normal cartilage cavities. processes in the synovial membrane that are especially prominent. Not only does the tissue of this membrane become richer in cells and blood-vessels, and permeated with extravasations of blood and masses of pigment, but the membrane overgrows the edges of the d ARTHRITIS DEFORMANS 369 joints, and thus covers more and more of the surface of the articular cartilage in the form of a pannus-like layer (a), leading to the gradual destruction of the latter (arthritis pannosa). The disappearance of the cartilage in this process is effected by the penetration in the first place of the growing synovial membrane into the cartilage cavities, converting the latter into pitted depressions (b), which progressively enlarge and finally coalesce. In the dilated cavities of the cartilage, instead of the normal cartilage cells large cells (c) are seen having an extraordinary number of processes, and regarding which it is only doubtful whether they are altered cartilage cells, or whether we have to do with cells of the synovial membrane that, having first penetrated into the cavities of the cartilage, are now enlarging them in all directions (chondroclasts ?). In addition to this peculiar growth of the synovial membrane, there may certainly also exist fibrillation of the cartilage and formation of warty cartilaginous and bony excrescences at the margins of the articular surfaces, but these changes as a rule are only subordinate in degree. A further peculiarity of the polyarticular form is that the synovial membrane not only covers the surface of the cartilage, but also sends highly-vascular processes to the articular cartilage opposite, in consequence of which the surfaces of the joint become partially or completely adherent to one another (fibrous ankylosis). The affected joint thus becomes fixed in a definite faulty position (flexion or hyperextension), and more or less immovable. Finally, the fibrous coating of the articular surfaces may ossify, and the fibrous then develops into an osseous ankylosis. In the monarticular form of arthritis deformans, the retrograde and hyperplastic changes in the articular ends of bones and the capsules of joints are combined in the most manifold fashions. In the first place, the fibrillation of the cartilage and synovial membrane here becomes prominent, attaining a very advanced degree, and being accompanied in the cartilage by a considerable growth of the cells, and by their transformation at the same time into large parentcells. The fibrillated portions of cartilage are next rubbed off in the movements of the joint, so that deficiencies are left which are either filled up again by processes of the synovial membrane, or become deeper and deeper, and finally lay bare the bone. The latter may then sclerose, owing to processes of ossification in its medullary spaces (cburnation), whilst its denuded surface is as it it were polished by the movements of the joint, and may even have grooves ground on it. In other parts of the articular ends of bones, again, a very extensive lacunar liquefaction may take place, in consequence of which there may result an extensive destruction of the |