Arteries and 

 nerves of bone. 



34 CARTILAGE. BONE. TEETH. 



the cells of which have undergone the process of fatty 

 degeneration. 



Of the two varieties the red, or foetal marrow, is 

 more richly supplied with blood-vessels. 



The arteries of bone are derived from its perios- 

 teum; one class of them, the smaller vessels, pene- 

 trate the compact substance and pursue the same 

 course as the Haversian canals which they occupy ; 

 the other class, larger, and known as nutritious arte- 

 ries, enter separate canals of their own, and thus 

 reach the medullary cavities, where they terminate 

 by supplying the marrow and anastomosing with the 

 vessels of the first class. The veins, as a rule, present 

 the same calibre and pursue the same course as the 

 arteries with which they correspond ; in some instan- 

 ces, however, they assume a larger size and different 

 arrangement, as in the sinuses of the diploe, and of 

 the bodies of the vertebrae. Up to the present time 

 lymphatics have not been demonstrated in bone. Its 

 nerves, which are numerous, ordinarily follow the 

 course of the arteries, and supply the marrow as well 

 as the bone; before penetrating its substance they 

 give off branches to the periosteum. There is reason 

 to believe that they terminate by free extremities. 

 bon v e elopmont of ^ ne development and growth of bone is accom- 

 plished in two ways : by ossification of the cartila- 

 ginous skeleton of the fcetus / and by transformation 

 of the deeper layers of the periosteum. 



The first mode of development is best studied in 

 very thin sections of a young bone, made just at the 

 line of junction of the cartilage and bone. On exa- 

 mining, in the first place, the cartilaginous portion of 



