12 ELEMENTARY PHYSIOLOGY. 



lower maxillary. The teeth are set in sockets of 

 these maxillary bones. 



BONES OF THE TRUNK. 



The main body is called the trunk. The upper 

 part of the trunk is fitted to contain the lungs and the 

 heart. Its lower part contains .the stomach, liver and 

 bowels. 



The great pillar of the body is the spinal 

 column!** column. It bears aloft the head the 



crowning part of the whole structure. It 

 supports the great vital organs of the main body. 

 It is most wonderfully constructed with reference to 

 comfort and safety of life. Instead of being com- 

 posed of but one or a few bones, it is built up of 

 twenty-six pieces, which, while laid up one above the 

 other, are separated from each other by very elastic 

 cushions of cartilage. This does not only make the 

 back-bone capable of bending forward, backward and 

 sideways, but it makes the whole pillar springy, so 

 that the delicate brain which rides at its summit is 

 not affected by jarring from the heavy movements of 

 the body. 



Twenty-four of the bones of the spinal 



column, or back, are called veriebrce 

 These are firmly bound together by ligaments and 

 interlocked with each other by their own projecting 

 parts. An opening runs through each vertebra. 

 These openings form the spinal canal through which 



