PHYSIOLOGY AND ANATOMY. — 19 
serves as a pillar or column for the support of our bodies. 
They inerease in size from the neck down, The skull is 
united to the upper vertebre by means of a joint, called the 
hinge joint, to enable us to move the head upward and 
downward—and what is called the ball-and-socket joint. 
In all the joints, the ends of the bones which work together 
are tipped with gristle, that they may move easily. The 
spinal marrow passes through the spine, and if this be once 
broken, the limbs below would become numb and motionless, 
and life would soon-end. : 
There is an innumerable 
number of nerves passing 
from this spinal cord to the 
_ stomach, to the heart, the . 
liver, and to every partof © ~~ 4 
the body. Joined to the | 
spine, 6, b, are twelve ribs 
on each side, seven of 
which are united to the 
sternum or breast-bone in 
front, that is composed of 
three small pieces of bone, 
which, although distinct at 
first, finally unite together, 
making one bone—these 
are called the true-ribs; 
then there are five which 
unite with the breast-bone 
by means of soft cartilages. 
“RIBS AND SPINE. 
