X. 



DISEASES OF THE BONES. 



Diseases of the bones are classed under two heads — inflamma- 

 tory and non-inflammatory — but the line of demarcation is not 

 very well defined. The process of inflammation takes place in 

 bone the same as in soft tissues. On making a section of a bone 

 compact and cancellated tissue is found. The compact tissue con- 

 tains the Haversian canals, conveying blood plasma to the lacunae. 

 In this manner this portion of the bone receives its supply of 

 nutritious material from the blood; without this arrangement the 

 bony structure could not receive nutrition. It will be seen that 

 the compact bone is abundantly provided with vessels, entering 

 from numerous points, covered by periosteum and endosteum; 

 that the^e nutrient vessels are exceedingly small; in conse(pience 

 of this the inflammatory process is very distinct and the symp- 

 toms very acute. Inflammation of the substance of the bone is 

 termed ostitis. Superficial ostitis is often associated with perios- 

 titis, or inflammation of the periosteum. In fact, the bone and 

 periosteum are so closely related t]\iit inflammation of the one 

 will involve the other. The first effect of inflammation is to in- 

 crease the size of the Haversian canals, which become more 

 irregular in size and outline. The earthy salts are partially re- 

 moved, and their place is filled by the products of inflammation. 

 An external swelling makes its appearance; the vessels of the 

 periosteum and soft parts becoming involved, throw out a deposit 

 upon the surface of the bone. This exudate, as a rule, becomes 

 converted into bone, leaving the parts permanently altered in 

 shape and appearance, or it may become absorbed before it is 

 ossified and the parts regain their former condition. "When 

 ossific matter is thrown out it is called exostosis, meaning bony 

 deposit, as splint, spavins, sore shins, etc. This exudate is at first 



(163) 



