"32 THE BONES AND JOINTS. 



substance. It is these secondary alterations in the basement substance 

 which lend to inflammations of the bone their most peculiar characters, 

 and in the prominence which these assume the fundamental alterations 

 are often overlooked. The most common of these secondary alter- 

 ations are the absorption of the hard basement substance of the bone and 

 its replacement by, or conversion into, young cellular forms of fibrillar 

 connective tissue or marrow tissue, and the new formation, in a more or 

 less typical manner, of new bone. As a result of these changes the bone 

 in simple inflammation becomes more vascular, and, with an increase of 

 spaces filled with granulation or marrow tissue, more porous at the 

 expense of the dense basement substance. Or the new-formed spaces 

 or the marrow cavities may be constantly encroached upon by the new- 

 formed bone lamellae on their walls, so that the bone becomes more com- 

 pact. Or, as is frequently the case, both series of changes occur either 

 simultaneously in different regions, or follow each other, or are vari- 

 ously associated together. Very frequently one or the other of the oppos- 

 ing forms of alteration predominates, or one may occur to the exclusion 

 of the other, and we thus have two prominent forms of inflammation, 

 which are called rarefying osteitis or osteo-porosis, and condensing osteitis or 

 osteo- sclerosis. The exact nature of the conditions under which in one 

 case the bones become more, in another less dense, we do not understand. 

 Furthermore, more or less characteristic forms of inflammation may occur 

 in syphilitic and tuberculous infection syphilitic and tuberculous osteitis. 

 Suppurative osteitis may further complicate the process. 



In addition to these phases of inflammation in bone, and in frequeut 

 and varied association with them, there are alterations leading to death 

 and destruction of bone tissue in greater or less amount, which are called 

 caries and necrosis. Finally, any of these forms, and commonly several 

 of them at once, are variously associated with more or less marked 

 inflammatory or degenerative alterations of the periosteum on the one 

 hand, or the marrow tissue on the other, or of both combined. 



Rarefying Osteitis consists essentially in the formation in the marrow 

 spaces, Haversian canals, or beneath the periosteum, of new, very cel- 

 lular and vascular tissue, resembling granulation or young marrow tissue, 

 under whose influence the basement substance of the bone is absorbed. 

 This absorption of the bone takes place largely as bone is absorbed in 

 normal growth, namely, under the influence of certain large cells, which 

 are grouped around the blood-vessels. If a thin section of bone which 

 is undergoing absorption be examined (Fig. 485), the edges of the bone 

 which border on the vascular surfaces are found irregularly indented by 

 deep or shallow depressions, sometimes simple, sometimes quite complex. 

 These are called Hoicship's lacunae and are usually filled or lined by larger 

 and smaller granular, frequently'multiuuclear cells the so-called osteo- 

 clasts. In the larger lacunas there may be granulation tissue with loops of 

 blood-vessels, with or without osteoclasts. Under the influence of the 

 osteoclasts or of the new vascular tissue, the bone is gradually ab- 

 sorbed. 



