180 OSSEOUS SYSTEM. 



them to resist fractures where they are most exposed to 

 them, and that the size of the bone may be reduced, where 

 such reduction is necessary, without injuring its strength. 



Q. What is the reticular texture of the bone? 



/#. It is a delicate modification of the cellular texture; 

 and it supports the medullary texture of the bones, and 

 offers points of insertion to the membrane of the medulla. 



Q. How is a light cellular structure at the ends of the 

 bones advantageous? 



/#. The weight of heavy compact structure at the ends 

 of the levers would be difficult to raise, and thereby im- 

 pede locomotion. 



Q. Where are the compact and cellular structures found 

 in the flat bones? 



/?. The compact is in the centre, the cellular is at the 

 periphery. 



Q. What texture prevails in the short bones? 



#. The cellular structure principally forms them. 



Q. Of what do the osseous protuberances consist? 



#. Principally of compact texture. 



Q. What are the elements which enter into the com- 

 position of the osseous texture? 



t/?. A calcareous and gelatinous substance. 



Q. What is this calcareous substance? 



/?. It is the phosphate of lime; and there are a few 

 other unimportant saline matters that enter into the com- 

 position of bone. 



Q. Is the proportion of the constituent parts of bony 

 structure uniform ? 



/?. It is not; on the contrary, it varies much. The teeth 

 have much more earthy substance than other bones. 



