122 THE BONES. 
What are the changes produced by tubercular and syphilitic 
osteitis ? 
The changes are the same as in a rarifying osteitis with the added 
changes that are common to these two forms of inflammation. 
What is osteomyelitis ? 
It is usually a suppurative inflammation of the marrow of bone, and 
may be due to idiopathic or traumatic causes. As the different parts of 
bone are so intimately connected they are all more or less affected. The 
periosteum may be swollen and succulent, and may be the seat of 
abscesses. The bony tissue itself may as a result be more or leas 
necrosed. ; 
What is necrosis of bone ? 
It is a death of portions of bone and a real gangrenous condition. 
When the circulation is cut off from a certain portion of bone it dies, 
but from its hardness it retains its outward structural appearances. An 
inflammatory change similar to that in rarifying osteitis is set up 
between the living and dead bone, and finally causes a complete 
separation. The dead bone or sequestrum may be absorbed or layers 
of new bony tissue may formed about it. 
How does caries differ from necrosis ? 
Caries is an ulceration of the bone with a molecular destruction of 
the bony tissue. While necrosis is a death of a mass or masses of 
bony tissue. 
What is rachitis and what are the microscopical changes in bony 
tissue in this disease ? 
It is a disease affecting the formation and development of bone. 
Microscopically the cells in the cartilage preceding bony formation are 
irregularly arranged. The zone of ossification, and the spaces in the 
newly-formed bone are irregular. As these spaces are irregular in size 
and shape the bone is not as strong as normal and may be spongy. 
What is osteomalacia ? 
It is a condition in which there is a gradual absorption of the 
inorganic salts of the bony tissue. As the salts are removed the fibrous 
basement substance and cells of the bone are left. This may become 
degenerated and followed by a growth of granulation tissue. 
What tumors have been seen in bone ? 
Fibromata, myxomata, osteomata, chondromata, sarcomata angio- 
mata and carcinomata. 
