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, „ „ m . 
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 tu Sh t 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. 8.—Frontal Bone of Human Skull under the fine tubes, OF Canaliculi. 
microscope,showing lacunas and canaliculi. These represent the 
spaces occupied by the original cells of the bone, and 
differ in shape and size in different animals. 
