212 



HEALTH AND DISEASE 



Fig-. 320. —Chronic O-stitis 



A, Lower portion of Radius of horse, showing results of Chronic Ostitis. B, Section of the same, 

 showing hard, dense condition of the bone. 



NECROSIS AND CARIES 



When bone is so far damaged by disease or accident as to cause it 

 to die, it is said to be affected with necrosis or caries, one or the other, 

 according to the mode of death. If a considerable quantity of the tissue 

 be destroyed at one time the term "necrosis" is used, but if the bone 

 gradually melts away or breaks down into minute particles during a 

 progressive ulceration it is spoken of as "caries". 



Necrosis. — Causes. The more common causes of necrosis as it affects 

 horses are blows and bruises dii'ectly applied to the bone; hence it occurs 

 that those bones or parts of bones most superficially placed, and conse- 

 quently most exposed to injury, are especially liable to the disease. Bones 

 deeper seated and enveloped in thick layers of muscle are comparatively 



