THE BONY SKELETON. 45 
cranium. By their union these bones form five cavities, which contain 
and protect the organs of sight, smell, and taste. The two principal 
bones are the upper maxillary! or jaw bones, marked 8 on fig. 41, 
Overlapping, and joined to them at the sides, are the two malar? or 
cheek bones, marked 6. These are joined behind to the two palate? 
bones, which form the back part of the roof of the mouth. The inside 
walls of the cavities for the eyes are partly formed by two small bones, 
called the lachrymal* bones, because there are holes through them for 
the passage of the ducts or canals which convey the tears from the 
eyes to the nose. The greater part of the nose is formed of cartilage 
or gristle, so that the bony part, formed of the two nasal bones, marked 
7,is not very prominent. The nasal cavity is divided into two by a 
partition, which is partly formed by a bone called the vomer,® from its 
resemblance to a ploughshare; and its outer walls are formed of two 
small turbinated® bones, which are thin bony plates, in the form of a 
scroll or horn, the use of which will be explained when we treat of the 2 
organ of smell. Last of all, comes the lower mawillary or lower jawbone, 
marked 9. 
2. The Trunk.—The most important part of the trunk is the Sprnn? or 
backbone, so called from its spikes or points. It consists of a large 
number of small pieces so jointed together as to make it exceed- 
ingly flexible. Each of the pieces is called a vertebra [Latin, ‘a joint’), Ad 
and is attached to the two between which it lies by strong elastic 
ligaments ;® while between each pair is a cushion of cartilage, which is 
thickest in the lower part of the spine, and serves a very important 
purpose. When the body is jolted_in any way, for example, in jumping /). 
from a height, these cushions act like the buffers of a railway train, and 
neutralise the shock. From its being composed of these vertebra, the 
spine is called the vertebral column. Each vertebra is perforated with a 
round hole; and from the manner in which they are joined together, 
these holes form a continuous canal, which contains and protects the 
spinal cord. ‘This substance, although sometimes erroneously called the 
spinal marrow, is quite distinct from the real marrow found in the long 
bones of the legs and arms. It is, in fact, next to the brain, the most 
important part of the nervous system, in connection with which it will 
afterwards be described. Behind the backbone are three rows of pro- 
jections ; one in the centre, forming the ridge felt along the back, and 
‘seen farthest to the right in the figure, called the spinous processes; 
and one on each side of these, called the transverse processes. In the whole 
1 From Latin mazilla, diminutive of mala, a jaw. 2 From Latin mala, a jaw. 
3 From Latin palatum, the roof of the mouth. 4 From Latin lachryma, a tear. 
5 Latin vomer, a ploughshare. 6 From Latin turbo, turbinis, a whirl. 
7 Latin spina, a thorn, 8 From Latin Jigo, to bind. 
