OSSEOUS TISSUE. 335 



In most osteophytes (puerperal or otherwise), there is an excess of 

 osteine and carbonate of lime above the normal standard. Very 

 likely, however, they approximate more nearly to true bone in pro- 

 portion to the time since their first formation. The analyses of 

 exostoses tend to the same conclusion. 



In osteoporosis (dilatation of the cancelli and of the Haversian 

 canals), the resorption of the mineral matters proceeds more rapidly 

 than that of the osteine, and the cavities formed are filled with fluid 

 fat. 



In rachitis there is a relative deficiency of earthy matters, with 

 an absolute excess of the osteine; the latter remaining unchanged 

 in its nature. The assumption that the carbonate of lime is in- 

 creased in rachitis is incorrect. Nor can rachitis be conditional on 

 the occurrence of free acid in the bones, though the phosphate of 

 lime is often much diminished. 



In softening of bone in the adult (osteo-malacia), the earthy con- 

 stituents are more diminished than in any bone disease yet men- 

 tioned. A large portion also of the osteine is destroyed. The 

 brittle network of bony tissue remaining, floats in thin, fluid fat, 

 sometimes amounting to twenty or thirty per cent. C. Schmidt 

 proved the existence of free lactic acid in the fluid of the long 

 bones. This may, however, be the result and not the cause of the 

 breaking down of the bone into fragments a chemical process 

 having occurred in the latter. 



In caries, the earthy matters most rapidly disappear, and the ca- 

 vity formed is filled with fat. 



Properties and Uses of the Osseous Tissue. 



The characteristic properties of osseous tissue are its hardness, 

 density, and rigidity due to the earthy constituents; and its elasti- 

 city and flexibility, dependent upon the osteine. It manifests no 

 vital properties, except so far as to secure its own nutrition and 

 reparation. 



The uses of the bones will be specified after their structure is 

 described, in the second section of this chapter. 



Distribution of the Osseous Tissue. 

 The osseous tissue is found : 



1. In the bones, of which the skeleton is composed; to which the 

 ossicula auditus, and the os hyoides also belong. 



2. In the bones developed in the tendons; as the sesamoid bones, 

 patella, &c. 



3. In the cementum of the teeth. 



Many of the cartilages also ossify pretty regularly as age ad- 

 vances ; as the costal cartilages, and those of the larynx. 



