CHAPTER IV. 



THE STRUCTURE, COMPOSITION AND HYGIENE OF 



BONES. 



The gross structure of bones. Although the bones 

 differ very much iii shape all are alike in microscopic 

 structure and in chemical composition. When alive they 

 have a bluish-white color,' with a pinkish hue when blood 

 is flowing through them ; they possess considerable flexi- 

 bility and elasticity, which may be best observed in a long 

 slender bone, as a rib.* 



To get a general idea of the structure of a bone we 

 may select the burner us (Fig. 21). When fresh this is 

 closely invested on its outside by a tough membrane, the 

 periosteum, composed of connective tissue and containing 

 many blood-vessels. On its under side new bony tissue is de- 

 posited as long as the bone is growing thicker, and through- 

 out life it is concerned in the nourishment of the bone, 



How do bones differ from one another? In what respeets do all 

 bones agree? What is the color of a living bone? Name some mechan- 

 ical properties of bone. In what bones may such properties be most 

 readily seen? 



Whnt covers a bone on the exterior? What is it composed of? 

 Does it contain bloodvessels? 



* The rib of a sheep or a rabbit when thoroughly boiled can be readily scraped 

 clean and preserved, and serves admirably to show the flexibility and elasticity of 

 bone. 



[47] 



