DISEASES OP BONES 183 



What forms of osteitis are of interest to the surgeon ? 



(1) Rarefying osteitis, (2) ossifying osteitis, (3) fungous 

 osteitis, (4) deforming osteitis. 



Describe rarefying osteitis. 



This form of osseous inflammation is also known as 

 osteoporosis. It is a degenerative osteitis, and usually the 

 result of intensive or infectious processes ; it may exist alone 

 or in combination with ossifying osteitis — that is, certain 

 centers may exhibit a rarefying osteitis while the adjacent 

 bony tissue undergoes an ossifying osteitis. Rarefying 

 osteitis serves also to limit infectious processes, and further, 

 to expel necrotic bone. 



Describe the changes talcing place in the osseous tissue in 

 rarefying osteitis. 

 Following the inflammation there is an exudate. This 

 exudate enters the Haversian canal, spaces and canaliculi; 

 proliferation of the cellular elements takes place and thus 

 embryonic tissue formation. As the result of the action of 

 the osteoclasts, the bone undergoes rarefaction — that is, 

 thinning ; granulation tissue becomes more and more abund- 

 ant, gradually taking the place from which the bony sub- 

 stance has been removed by the osteoclasts. The solution 

 and removal of the bone does not occur uniformly, but 

 irregularly here and there. 



Describe ossifying osteitis. 



This form of bony inflammation is also known as osteo- 

 sclerosis. It is the opposite of rarefying osteitis, as it repre- 

 sents a regenerative process and is usually the result of 

 slighter and continuous — that is, chronic — irritations. Ossi- 

 fying osteitis serves to render denser and stronger bony tissue 



