THE OSSEOUS TISSUE. 



161 



calls the helicine, that penetrate the cavernous substance 

 and end abruptly in the venous cells, which he regards as 

 chiefly concerned in the erection, but whose existence is 

 denied by Valentin. 



FIG. 30. 



CHAPTER XII. 



THE OSSEOUS TISSUE. 



ANALYSIS. 



DEFINITION, COMPOSITION, SKELETON, DIVISIONS, NUMBER, SITUATION, DENSITY, 

 STRENGTH, SURFACE, STRUCTURE, DEVELOPMENT, GROWTH, CALLUS. 



THE ~bones are the hardest of all the tissues; they consti- 

 tute the solid frame-work of the body, are the passive organs 

 of locomotion, give attachment to a variety of muscles, and 

 afford protection to numerous viscera. 



Bone consists essentially of two 

 parts, an earthy and an animal ; the 

 earthy being chiefly phosphate of 

 lime, the animal mainly gelatin. By 

 subjecting bone to fire, the animal 

 portion is consumed and the earthy 

 left ; presenting, however, the perfect 

 shape of the bone, but being very brit- 

 tle, easily reduced to powder and pre- 

 senting the honey-comb appearance. 

 When put in dilute muriatic acid, 

 about 1 part of acid to 30 of water, 

 the earthy portion is removed and 

 the animal left, which also retains 

 the original shape of the bone. The chemical analysis of 

 bone, according to Berzelius, makes it consist of 



FIG. 30 represents the texture of bone after maceration in dilute acid, a a, 

 compact matter. 6 6 The same split up, so as to show the longitudinal fibres 

 Composing it. c Internal cellular or cancellated structure, d Bone seen under 

 its articular cartilage. 

 11 



