THE BONES AND JOINTS. 735 



old people and may be of long duration. They may gradually enlarge 

 and be accompanied by an ossifying periostitis, so that the bone is ex- 

 panded. The abscesses in suppurative osteitis sometimes develop rapidly 

 and may perforate. On the other hand, instead of abscesses, there may 

 be a diffuse infiltration with pus of the Haversiau canals or of the spaces 

 formed by rarefying osteitis (see Osteomyelitis, below). 



Osteomyelitis. The tissues of the medulla so frequently share in the 

 inflammatory processes in bone that many conditions described as osteitis 

 are really osteomyelitis. It is customary, however, to reserve the latter 

 name for those cases in which the medulla is primarily or chiefly involved. 



ACUTE INFECTIOUS OSTEOMYELITIS. This may occur as the result 

 of a local injury which permits the access or favors the development of 

 pyogenic micro-organisms ; it may be metastatic, resulting from the trans- 

 portation of infectious material from other parts of the body in septi- 

 caemia and pyaemia, in typhoid fever, in the exanthematous fevers, and 

 under other conditions ; or it may occur without evidence of local predis- 

 position or of infectious processes in other parts of the body. 



The lesions of acute infectious osteomyelitis are, in the large majority 

 of cases at least, due to the presence and action of the pyogenic cocci, 

 the Staphylococcus pyogenes and the Streptococcus pyogenes, and in 

 many of its forms it may be regarded as one of the phases of septicaemia 

 or septico- pyaemia. 



While the lesions vary widely, the following general description is 

 applicable to a considerable proportion of the cases: 



At the commencement of the disease, which usually begins in the shaft 

 of one of the long bones, there are hyperaemia and oedema of the medulla, 

 so that if the bone be opened the marrow is soft and of a dark-red color. 

 A diffuse suppuration now rapidly ensues, and the marrow becomes 

 streaked or mottled with gray. Occasionally, though not often, larger 

 and smaller abscesses may form in the marrow. The inflammatory areas 

 may be circumscribed ; or, in the more malignant cases, the entire mar- 

 row may become rapidly involved. The cancellous tissue of one or both 

 of the epiphyses usually becomes involved. The disease, however, is 

 not commonly confined to the medullary spaces. The periosteum becomes 

 oedematous and infiltrated with pus, and the surrounding soft parts may 

 become the seat of intense inflammatory changes. Abscesses of the peri- 

 osteum or surrounding tissues are apt to form. As a result of these 

 changes, necrosis of greater or less portions of the bone may ensue. The 

 medullary cavity may become enlarged as pus accumulates, and the wall 

 of the bone may be broken through, permitting the discharge of pus out- 

 ward. Sometimes several bones are involved at once. Secondary in- 

 volvement of the joints is very frequent. Here there may be only a 

 serous or purulent exudation ; or the acute and destructive inflammatory 

 process may extend beneath the joint and produce extensive alterations. 

 In young persons the epiphyses very frequently become separated from 

 the shaft by the destruction of the cartilage which binds them together. 



In the severer cases, which are often called, par excellence, malignant 



