ORGANIZATION. 37 



age of the animal. If a chicken-bone be left in dilute 

 muriatic acid several days, it may be tied into a knot, since 

 the acid has dissolved 

 the lime, leaving noth- 

 ing but cartilage and 

 connective tissue. If a 

 bone be burned, it be- 

 comes light, porous, and 

 brittle, the lime alone 

 remaining. 15 



Bone is a very vas- 

 cular tissue; that is, it 

 is traversed by minute ^_^_ 



blood-vessels and nerves, FIQ 7 _ Trausverse "on^Ta Bone (Human 

 Which paSS through a Femur), x 50, showiug Haversian canals. 



net-work of tubes, called Haversian canals. The canals 

 average y^ of an inch, being finest near the surface of 

 the bone, and larger further in, where they form a cancel- 

 lated or spongy structure, and finally merge (in the long 



bones) into the central 

 cavity, containing the 

 marrow. Under the 

 microscope, each canal 

 appears to be the cen- 

 tre of a multitude of 

 laminae, or plates, ar- 

 ranged around it. Ly- 

 ing between these plates 

 are little cavities, called 

 lacunae, which are con- 

 nected by exceedingly 



FIG. S.-Frontal Bone of Human Skull under the fine tllbeS,Or CanallCuli. 

 microscope, showing lacunae and canaliculi. These represent the 



spaces occupied by the original cells of the bone, and 

 differ in shape and size in different animals. 



