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, _ 



7 Fig. 7.— Transverse section of a Bone (Human 

 which paSS through a Femur), x 50, showing Haversian canals. 



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

 average tq-W 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 



the 



cavity, containing 

 marrow* Under the 

 microscope, each canal 

 appears to be the cen- 

 tre of a multitude of 

 lamince, or plates, ar- 

 ranged around it. Ly- 

 ing between these plates 

 are little cavities, called 

 lacunce, from which ra- 

 diate exceedingly fine 

 or canaliculi. 

 represent the 

 original cells of the bone, and differ in shape and size in 

 different animals. • 



Fig. 8.— Frontal Cone of Human Skull under the P ores j 

 microscope, showing lacuni and canaliculi. These 



